Multimedia distribution system

ABSTRACT

A multimedia file and methods of generating, distributing and using the multimedia file are described. Multimedia files in accordance with embodiments of the present invention can contain multiple video tracks, multiple audio tracks, multiple subtitle tracks, a complete index that can be used to locate each data chunk in each of these tracks and an abridged index that can enable the location of a subset of the data chunks in each track, data that can be used to generate a menu interface to access the contents of the file and ‘meta data’ concerning the contents of the file. Multimedia files in accordance with several embodiments of the present invention also include references to video tracks, audio tracks, subtitle tracks and ‘meta data’ external to the file. One embodiment of a multimedia file in accordance with the present invention includes a series of encoded video frames, a first index that includes information indicative of the location within the file and characteristics of each encoded video frame and a separate second index that includes information indicative of the location within the file of a subset of the encoded video frames.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation-in-part of U.S. patentapplication Ser. No. 11/016,184, filed on Dec. 17, 2004, entitledMULTIMEDIA DISTRIBUTION SYSTEM, which is a continuation-in-part of U.S.patent application Ser. No. 10/731,809, filed on Dec. 8, 2003, entitledFILE FORMAT FOR MULTIPLE TRACK DIGITAL DATA, and also claims priorityfrom Patent Cooperation Treaty Patent Application No. PCT/US2004/041667,filed on Dec. 8, 2004, entitled MULTIMEDIA DISTRIBUTION SYSTEM, thedisclosures of which are incorporated herein by reference in theirentirety.

BACKGROUND OF THE INVENTION

The present invention relates generally to encoding, transmission anddecoding of multimedia files. More specifically, the invention relatesto the encoding, transmission and decoding of multimedia files that caninclude tracks in addition to a single audio track and a single videotrack.

The development of the internet has prompted the development of fileformats for multimedia information to enable standardized generation,distribution and display of multimedia information. Typically, a singlemultimedia file includes a single video track and a single audio track.When multimedia is written to a high volume and physically transportablemedium, such as a CD-R, multiple files can be used to provide a numberof video tracks, audio tracks and subtitle tracks. Additional files canbe provided containing information that can be used to generate aninteractive menu.

SUMMARY OF THE INVENTION

Embodiments of the present invention include multimedia files andsystems for generating, distributing and decoding multimedia files. Inone aspect of the invention, the multimedia files include a plurality ofencoded video tracks. In another aspect of the invention, the multimediafiles include a plurality of encoded audio tracks. In another aspect ofthe invention, the multimedia files include at least one subtitle track.In another aspect of the invention, the multimedia files include encodedinformation indexing the audio, video and/or subtitle tracks.

In one embodiment, the invention includes a series of encoded videoframes, a first index that includes information indicative of thelocation within the file and characteristics of each encoded videoframe, a separate second index that includes information indicative ofthe location within the file of a subset of the encoded video frames.

In a further embodiment, the second index includes at least one tag thatreferences an encoded video frame in the subset of encoded video framesand each tag includes the location within the file of the referencedencoded video frame and the frame number of the encoded video frame inthe sequence of encoded video frames.

Another embodiment also includes at least one audio track. In addition,each tag further comprises a reference to a portion of at least one ofthe audio tracks and the portion of the track that is referencedaccompanies the encoded video frame referenced by the tag.

In a still further embodiment, each tag further comprises a reference toinformation located within the first index and the informationreferenced in the first index is indicative of the location within thefile and characteristics of the encoded video frame referenced by thetag.

Still another embodiment includes a processor and a memory including afile containing at least one sequence of encoded video frames. Inaddition, the processor is configured to generate an abridged index thatreferences a subset of the encoded video frames in the sequence ofencoded video frames.

In a yet further embodiment, the processor is configured to generate acomplete index that references all of the encoded video frames in thesequence of encoded video frames and each reference to an encoded videoframe in the abridged index includes a reference to the reference tothat frame in the complete index.

In yet another embodiment, each reference to an encoded video frame inthe abridged index includes the sequence number of the encoded videoframe.

In further embodiment again, the processor is configured to include ineach reference to an encoded video frame a reference to a locationwithin at least one sound track.

Another embodiment again includes a processor and a memory containing amultimedia file. In addition, the multimedia file includes a sequence ofencoded video frames, a complete index referencing each encoded videoframe in the sequence of encoded video frames and an abridged indexreferencing a subset of the encoded video frames in the sequence ofencoded video frames. Furthermore, the processor is configured to locatea particular encoded video frame within the multimedia file using theabridged index.

In a further additional embodiment, the processor is configured tolocate reference information in the complete index using the abridgedindex.

In another additional embodiment, the multimedia file includes at leastone audio track accompanying the sequence of encoded video frames andeach reference to an encoded video frame in the abridged index includesa reference to a portion of at least one of the video tracks.

An embodiment of the method of the invention includes obtaining asequence of encoded video frames, identifying a subset of frames fromthe sequence of encoded video frames and generating an abridged indexthat references the location within the multimedia file of each encodedvideo frame in the subset of encoded video frames.

In a further embodiment of the method of the invention, the generationof an abridged index further includes generating a reference to thelocation of each encoded video frame within the subset of encoded videoframes and recording the sequence number of each encoded video framewithin the subset of encoded video frames.

Another embodiment of the method of the invention also includesobtaining at least one audio track accompanying the sequence of encodedvideo frames. In addition, the generation of an abridged index furthercomprises associating with each referenced encoded video frame areference to a location with at least one of the audio tracks.

A still further embodiment of the method of the invention also includesobtaining a complete index that includes a reference to each encodedvideo frame in the sequence of encoded video frames. In addition, thegeneration of an index further comprises associating with eachreferenced encoded video frame a reference to a location within thesecond index.

Still another embodiment of the method of the invention includesidentifying a desired encoded video frame, determining the encoded videoframe that is closest to the desired video frame in the second index anddisplaying an encoded video frame.

In a yet further embodiment of the method of the invention, eachreference in the second index to an encoded video frame also includes areference to the portion of the first index that refers to that encodedvideo frame, displaying an encoded video frame, further includes usingthe reference to the encoded video frame in the second index that isclosest to the desired encoded video frame to locate that encoded framewithin the first index, searching in the first index for the desiredencoded video frame and displaying the desired encoded video frame.

In yet another embodiment of the method of the invention, the closestframe is the closest preceding frame in the sequence to the desiredframe.

In a further additional embodiment of the invention, displaying anencoded video frame further includes displaying the encoded video framethat is determined to be closest to the desired video frame.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1. is a diagram of a system in accordance with an embodiment of thepresent invention for encoding, distributing and decoding files.

FIG. 2.0. is a diagram of the structure of a multimedia file inaccordance with an embodiment of the present invention.

FIG. 2.0.1. is a diagram of the structure of a multimedia file inaccordance with another embodiment of the present invention.

FIG. 2.1. is a conceptual diagram of a ‘hdrl’ list chunk in accordancewith one embodiment of the invention.

FIG. 2.2. is a conceptual diagram of a ‘strl’ chunk in accordance withan embodiment of the invention.

FIG. 2.3. is a conceptual diagram of the memory allocated to store a‘DXDT’ chunk of a multimedia file in accordance with an embodiment ofthe invention.

FIG. 2.3.1. is a conceptual diagram of ‘meta data’ chunks that can beincluded in a ‘DXDT’ chunk of a multimedia file in accordance with anembodiment of the invention.

FIG. 2.3.2. is a conceptual diagram of an ‘index’ chunk that can beincluded in a ‘DXDT’ chunk of a multimedia file in accordance with anembodiment of the invention.

FIG. 2.4. is a conceptual diagram of the ‘DMNU’ chunk in accordance withan embodiment of the invention.

FIG. 2.5. is a conceptual diagram of menu chunks contained in a‘WowMenuManager’ chunk in accordance with an embodiment of theinvention.

FIG. 2.6. is a conceptual diagram of menu chunks contained within a‘WowMenuManager’ chunk in accordance with another embodiment of theinvention.

FIG. 2.6.1. is a conceptual diagram illustrating the relationshipsbetween the various chunks contained within a ‘DMNU’ chunk.

FIG. 2.7. is a conceptual diagram of the ‘movi’ list chunk of amultimedia file in accordance with an embodiment of the invention.

FIG. 2.8. is a conceptual diagram of the ‘movi’ list chunk of amultimedia file in accordance with an embodiment of the invention thatincludes DRM.

FIG. 2.9. is a conceptual diagram of the ‘DRM’ chunk in accordance withan embodiment of the invention.

FIG. 3.0. is a block diagram of a system for generating a multimediafile in accordance with an embodiment of the invention.

FIG. 3.1. is a block diagram of a system to generate a ‘DXDT’ chunk inaccordance with an embodiment of the invention.

FIG. 3.2. is a block diagram of a system to generate a ‘DMNU’ chunk inaccordance with an embodiment of the invention.

FIG. 3.3. is a conceptual diagram of a media model in accordance with anembodiment of the invention.

FIG. 3.3.1. is a conceptual diagram of objects from a media model thatcan be used to automatically generate a small menu in accordance with anembodiment of the invention.

FIG. 3.4. is a flowchart of a process that can be used to re-chunk audioin accordance with an embodiment of the invention.

FIG. 3.5. is a block diagram of a video encoder in accordance with anembodiment of the present.

FIG. 3.6. is a flowchart of a method of performing smoothnesspsychovisual enhancement on an I frame in accordance with embodiments ofthe invention.

FIG. 3.7. is a flowchart of a process for performing a macroblock SADpsychovisual enhancement in accordance with an embodiment of theinvention.

FIG. 3.8. is a flowchart of a process for one pass rate control inaccordance with an embodiment of the invention.

FIG. 3.9. is a flowchart of a process for performing Nth pass VBV ratecontrol in accordance with an embodiment of the invention.

FIG. 4.0. is a flowchart for a process for locating the requiredmultimedia information from a multimedia file and displaying themultimedia information in accordance with an embodiment of theinvention.

FIG. 4.0.1. is a flowchart showing a process for locating a specificencoded video frame within a multimedia file using an ‘index’ chunk inaccordance with an embodiment of the invention.

FIG. 4.0.2. is a flowchart showing a process for locating the ‘tag’chunk within an ‘index’ chunk that references the preceding frameclosest to a desired video frame within a video sequence in accordancewith an embodiment of the invention.

FIG. 4.1. is a block diagram of a decoder in accordance with anembodiment of the invention.

FIG. 4.2. is an example of a menu displayed in accordance with anembodiment of the invention.

FIG. 4.3. is a conceptual diagram showing the sources of informationused to generate the display shown in FIG. 4.2 in accordance with anembodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

Referring to the drawings, embodiments of the present invention arecapable of encoding, transmitting and decoding multimedia files.Multimedia files in accordance with embodiments of the present inventioncan contain multiple video tracks, multiple audio tracks, multiplesubtitle tracks, a complete index that can be used to locate each datachunk in each of the tracks and an abridged index that can be used tolocate a subset of the data chunks in each track, data that can be usedto generate a menu interface to access the contents of the file and‘meta data’ concerning the contents of the file. Multimedia files inaccordance with several embodiments of the present invention alsoinclude references to video tracks, audio tracks, subtitle tracks and‘meta data’ external to the file.

1. Description of System

Turning now to FIG. 1, a system in accordance with an embodiment of thepresent invention for encoding, distributing and decoding files isshown. The system 10 includes a computer 12, which is connected to avariety of other computing devices via a network 14. Devices that can beconnected to the network include a server 16, a consumer electronics(CE) device 17, a lap-top computer 18 and a personal digital assistant(PDA) 20. In various embodiments, the connections between the devicesand the network can be either wired or wireless and implemented usingany of a variety of networking protocols.

In operation, the computer 12 can be used to encode multimedia files inaccordance with an embodiment of the present invention. The computer 12can also be used to decode multimedia files in accordance withembodiments of the present invention and distribute multimedia files inaccordance with embodiments of the present invention. The computer candistribute files using any of a variety of file transfer protocolsincluding via a peer-to-peer network. In addition, the computer 12 cantransfer multimedia files in accordance with embodiments of the presentinvention to a server 18, where the files can be accessed by otherdevices. The other devices can include any variety of computing deviceor even a dedicated decoder device. In the illustrated embodiment, aset-top cable box, a lap-top computer and a PDA are shown. In otherembodiments, various types of digital set-top boxes, desk-top computers,game machines, CE devices and other devices can be connected to thenetwork, download the multimedia files and decode them.

In one embodiment, the devices access the multimedia files from theserver via the network. In other embodiments, the devices access themultimedia files from a number of computers via a peer-to-peer network.In several embodiments, multimedia files can be written to a portablestorage device such as a disk drive, CD-ROM or DVD. In many embodiments,electronic devices can access multimedia files written to portablestorage devices.

2. Description of File Structure

Multimedia files in accordance with embodiments of the present inventioncan be structured to be compliant with the Resource Interchange FileFormat (‘RIFF file format’), defined by Microsoft Corporation ofRedmond, Wash. and International Business Machines Corporation ofArmonk, N.Y. RIFF is a file format for storing multimedia data andassociated information. A RIFF file typically has an 8-byte RIFF header,which identifies the file and provides the residual length of the fileafter the header (i.e. file_length-8). The entire remainder of the RIFFfile comprises “chunks” and “lists.” Each chunk has an 8-byte chunkheader identifying the type of chunk, and giving the length in bytes ofthe data following the chunk header. Each list has an 8-byte list headeridentifying the type of list and giving the length in bytes of the datafollowing the list header. The data in a list comprises chunks and/orother lists (which in turn may comprise chunks and/or other lists). RIFFlists are also sometimes referred to as “list chunks.”

An AVI file is a special form of RIFF file that follow the format of aRIFF file, but include various chunks and lists with defined identifiersthat contain multimedia data in particular formats. The AVI format wasdeveloped and defined by Microsoft Corporation. AVI files are typicallycreated using a encoder that can output multimedia data in the AVIformat. AVI files are typically decoded by any of a group of softwarecollectively known as AVI decoders.

The RIFF and AVI formats are flexible in that they only define chunksand lists that are part of the defined file format, but allow files toalso include lists and/or chunks that are outside the RIFF and/or AVIfile format definitions without rendering the file unreadable by a RIFFand/or AVI decoder. In practice, AVI (and similarly RIFF) decoders areimplemented so that they simply ignore lists and chunks that containheader information not found in the AVI file format definition. The AVIdecoder must still read through these non-AVI chunks and lists and sothe operation of the AVI decoder may be slowed, but otherwise, theygenerally have no effect on and are ignored by an AVI decoder.

A multimedia file in accordance with an embodiment of the presentinvention is illustrated in FIG. 2.0. The illustrated multimedia file 30includes a character set chunk (‘CSET’ chunk) 32, an information listchunk (‘INFO’ list chunk) 34, a file header chunk (‘hdrl’ list chunk)36, a meta data chunk (‘DXDT’ chunk) 38, a menu chunk (‘DMNU’ chunk) 40,a junk chunk (‘junk’ chunk) 41, the movie list chunk (‘movi’ list chunk)42, an optional index chunk (‘idx1’ chunk) 44 and a second menu chunk(‘DMNU’ chunk) 46. Some of these chunks and portions of others aredefined in the AVI file format while others are not contained in the AVIfile format. In many, but not all, cases, the discussion belowidentifies chunks or portions of chunks that are defined as part of theAVI file format.

Another multimedia file in accordance with an embodiment of the presentinvention is shown in FIG. 2.0.1. The multimedia file 30′ is similar tothat shown in FIG. 2.0. except that the file includes multipleconcatenated ‘RIFF’ chunks. The ‘RIFF’ chunks can contain a ‘RIFF’ chunksimilar to that shown in FIG. 2.0. that can exclude the second ‘DMNU’chunk 46 or can contain menu information in the form of a ‘DMNU’ chunk46′.

In the illustrated embodiment, the multimedia file 30′ includes multipleconcatenated ‘RIFF’ chunks, where the first ‘RIFF’ chunk 50 includes acharacter set chunk (‘CSET’ chunk) 32′, an information list chunk(‘INFO’ list chunk) 34′, a file header chunk (‘hdrl’ list chunk) 36′, ameta data chunk (‘DXDT’ chunk) 38′, a menu chunk (‘DMNU’ chunk) 40′, ajunk chunk (‘junk’ chunk) 41′, the movie list chunk (‘movi’ list chunk)42′ and an optional index chunk (‘idx1’ chunk) 44′. The second ‘RIFF’chunk 52 contains a second menu chunk (‘DMNU’ chunk) 46′. Additional‘RIFF’ chunks 54 containing additional titles can be included after the‘RIFF’ menu chunk 52. The additional ‘RIFF’ chunks can containindependent media in compliant AVI file format. In one embodiment, thesecond menu chunk 46′ and the additional ‘RIFF’ chunks have specialized4 character codes (defined in the AVI format and discussed below) suchthat the first two characters of the 4 character codes appear as thesecond two characters and the second two characters of the 4 charactercodes appear as the first two characters.

2.1. The ‘CSET’ Chunk

The ‘CSET’ chunk 32 is a chunk defined in the Audio Video Interleavefile format (AVI file format), created by Microsoft Corporation. The‘CSET’ chunk defines the character set and language information of themultimedia file. Inclusion of a ‘CSET’ chunk in accordance withembodiments of the present invention is optional.

A multimedia file in accordance with one embodiment of the presentinvention does not use the ‘CSET’ chunk and uses UTF-8, which is definedby the Unicode Consortium, for the character set by default combinedwith RFC 3066 Language Specification, which is defined by InternetEngineering Task Force for the language information.

2.2. The ‘INFO’ List Chunk

The ‘INFO’ list chunk 34 can store information that helps identify thecontents of the multimedia file. The ‘INFO’ list is defined in the AVIfile format and its inclusion in a multimedia file in accordance withembodiments of the present invention is optional. Many embodiments thatinclude a ‘DXDT’ chunk do not include an ‘INFO’ list chunk.

2.3. The ‘hdrl’ List Chunk

The ‘hdrl’ list chunk 38 is defined in the AVI file format and providesinformation concerning the format of the data in the multimedia file.Inclusion of a ‘hdrl’ list chunk or a chunk containing similardescription information is generally required. The ‘hdrl’ list chunkincludes a chunk for each video track, each audio track and eachsubtitle track.

A conceptual diagram of a ‘hdrl’ list chunk 38 in accordance with oneembodiment of the invention that includes a single video track 62, twoaudio tracks 64, an external audio track 66, two subtitle tracks 68 andan external subtitle track 70 is illustrated in FIG. 2.1. The ‘hdrl’list 60 includes an ‘avih’ chunk. The ‘avih’ chunk 60 contains globalinformation for the entire file, such as the number of streams withinthe file and the width and height of the video contained in themultimedia file. The ‘avih’ chunk can be implemented in accordance withthe AVI file format.

In addition to the ‘avih’ chunk, the ‘hdrl’ list includes a streamdescriptor list for each audio, video and subtitle track. In oneembodiment, the stream descriptor list is implemented using ‘strl’chunks. A ‘strl’ chunk in accordance with an embodiment of the presentinvention is illustrated in FIG. 2.2. Each ‘strl’ chunk serves todescribe each track in the multimedia file. The ‘strl’ chunks for theaudio, video and subtitle tracks within the multimedia file include a‘strl’ chunk that references a ‘strh’ chunk 92, a ‘strf’ chunk 94, a‘strd’ chunk 96 and a ‘strn’ chunk 98. All of these chunks can beimplemented in accordance with the AVI file format. Of particularinterest is the ‘strh’ chunk 92, which specifies the type of mediatrack, and the ‘strd’ chunk 96, which can be modified to indicatewhether the video is protected by digital rights management. Adiscussion of various implementations of digital rights management inaccordance with embodiments of the present invention is provided below.

Multimedia files in accordance with embodiments of the present inventioncan contain references to external files holding multimedia informationsuch as an additional audio track or an additional subtitle track. Thereferences to these tracks can either be contained in the ‘hdrl’ chunkor in the ‘junk’ chunk 41. In either case, the reference can becontained in the ‘strh’ chunk 92 of a ‘strl’ chunk 90, which referenceseither a local file or a file stored remotely. The referenced file canbe a standard AVI file or a multimedia file in accordance with anembodiment of the present invention containing the additional track.

In additional embodiments, the referenced file can contain any of thechunks that can be present in the referencing file including ‘DMNU’chunks, ‘DXDT’ chunks and chunks associated with audio, video and/orsubtitle tracks for a multimedia presentation. For example, a firstmultimedia file could include a ‘DMNU’ chunk (discussed in more detailbelow) that references a first multimedia presentation located withinthe ‘movi’ list chunk of the first multimedia file and a secondmultimedia presentation within the ‘movi’ list chunk of a secondmultimedia file. Alternatively, both ‘movi’ list chunks can be includedin the same multimedia file, which need not be the same file as the filein which the ‘DMNU’ chunk is located.

2.4. The ‘DXDT’ Chunk

The ‘DXDT’ chunk 38 contains so called ‘meta data’. ‘Meta data’ is aterm used to describe data that provides information about the contentsof a file, document or broadcast. The ‘meta data’ stored within the‘DXDT’ chunk of multimedia files in accordance with embodiments of thepresent invention can be used to store such content specific informationas title, author, copyright holder and cast. In addition, technicaldetails about the codec used to encode the multimedia file can beprovided such as the CLI options used and the quantizer distributionafter each pass.

In one embodiment, the meta data is represented within the ‘DXDT’ chunkas a series of statements, where each statement includes a subject, apredicate, an object and an authority. The subject is a reference towhat is being described. The subject can reference a file, item, personor organization. The subject can reference anything havingcharacteristics capable of description. The predicate identifies acharacteristic of the subject that is being described. The object is adescription of the identified characteristic of the subject and theauthority identifies the source of the information.

The following is a table showing an example of how various pieces of‘meta data’, can be represented as an object, a predicate, a subject andan authority:

TABLE 1 Conceptual representation of ‘meta data’ Subject PredicateObject Authority _:file281 http://purl.org/dc/elements/1.1/title ‘MovieTitle’ _:auth42 _:file281http://xmlns.divxnetworks.com/2004/11/cast#Person _:cast871 _:auth42_:file281 http://xmlns.divxnetworks.com/2004/11/cast#Person _:cast872_:auth42 _:file281 http://xmlns.divxnetworks.com/2004/11/cast#Person_:cast873 _:auth42 _:cast871http://xmlns.divxnetworks.com/2004/11/cast#name ‘Actor 1’ _:auth42_:cast871 http://xmlns.divxnetworks.com/2004/11/cast#role Actor _:auth42_:cast871 http://xmlns.divxnetworks.com/2004/11/cast#character‘Character Name 1’ _:auth42 _:cast282http://xmlns.divxnetworks.com/2004/11/cast#name ‘Director 1’ _:auth42_:cast282 http://xmlns.divxnetworks.com/2004/11/cast#role Director_:auth42 _:cast283 http://xmlns.divxnetworks.com/2004/11/cast#name‘Director 2’ _:auth42 _:cast283http://xmlns.divxnetworks.com/2004/11/cast#role Director _:auth42_:file281 http://purl.org/dc/elements/1.1/rights Copyright 1998 ‘StudioName’. _:auth42 All Rights Reserved. _:file281 Series _:file321 _:auth42_:file321 Episode 2 _:auth42 _:file321http://purl.org/dc/elements/1.1/title ‘Movie Title 2’ _:auth42 _:file321Series _:file122 _:auth42 _:file122 Episode 3 _:auth42 _:file122http://purl.org/dc/elements/1.1/title ‘Movie Title 3’ _:auth42 _:auth42http://xmlns.com/foaf/0.1/Organization _:foaf92 _:auth42 _:foaf92http://xmlns.com/foaf/0.1/name ‘Studio Name’ _:auth42 _:file281http://xmllns.divxnetworks.com/2004/11/track#track _:track#dc00 _:auth42_:track#dc00 http://xmlns.divxnetworks.com/2004/11/track#resolution 1024× 768 _:auth42 _:file281http://xmlns.divxnetworks.com/2004/11/content#certificationLevel HT_:auth42 _:track#dc00http://xmlns.divxnetworks.com/2004/11/track#frameTypeDist 32, 1, 3, 5_:auth42 _:track#dc00http://xmlns.divxnetworks.com/2004/11/track#codecSettings bv1 276-psy0-key 300-b 1-sc _:auth42 50-pq 5-vbv 6951200, 3145728, 2359296- profile3-nf

In one embodiment, the expression of the subject, predicate, object andauthority is implemented using binary representations of the data, whichcan be considered to form Directed-Labeled Graphs (DLGs). A DLG consistsof nodes that are either resources or literals. Resources areidentifiers, which can either be conformant to a naming convention suchas a Universal Resource Identifier (“URI”) as defined in RFC 2396 by theInternet Engineering Taskforce (http://www.ietf.org/rfc/rfc2396.txt) orrefer to data specific to the system itself. Literals arerepresentations of an actual value, rather than a reference.

An advantage of DLGs is that they allow the inclusion of a flexiblenumber of items of data that are of the same type, such as cast membersof a movie. In the example shown in Table 1, three cast members areincluded. However, any number of cast members can be included. DLGs alsoallow relational connections to other data types. In Table 1, there is a‘meta data’ item that has a subject “_:file281,” a predicate “Series,”and an object “_:file321.” The subject “_:file281” indicates that the‘meta data’ refers to the content of the file referenced as “_:file321”(in this case, a movie—“Movie Title 1”). The predicate is “Series,”indicating that the object will have information about another movie inthe series to which the first movie belongs. However, “_:file321” is notthe title or any other specific information about the series, but rathera reference to another entry that provides more information about“_:file321”. The next ‘meta data’ entry, with the subject “_:file321”,however, includes data about “_:file321,” namely that the Title asspecified by the Dublin Core Vocabulary as indicated by“http://purl.org/dc/elements/1.1/title” of this sequel is “Movie Title2.”

Additional ‘meta data’ statements in Table 1 specify that “Actor 1” wasa member of the cast playing the role of “Character Name 1” and thatthere are two directors. Technical information is also expressed in the‘meta data.’ The ‘meta data’ statements identify that “_:file281”includes track “_:track#dc00.” The ‘meta data’ provides informationincluding the resolution of the video track, the certification level ofthe video track and the codec settings. Although not shown in Table 1,the ‘meta data’ can also include a unique identifier assigned to a trackat the time of encoding. When unique identifiers are used, encoding thesame content multiple times will result in a different identifier foreach encoded version of the content. However, a copy of the encodedvideo track would retain the identifier of the track from which it wascopied.

The entries shown in Table 1 can be substituted with other vocabulariessuch as the UPnP vocabulary, which is defined by the UPnP forum (seehttp://www.upnpforum.org). Another alternative would be the Digital ItemDeclaration Language (DIDL) or DIDL-Lite vocabularies developed by theInternational Standards Organization as part of work towards the MPEG-21standard. The following are examples of predicates within the UPnPvocabulary:

urn:schemas-upnp-org:metadata-1-0/upnp/artist

urn:schemas-upnp-org:metadata-1-0/upnp/actor

urn:schemas-upnp-org:metadata-1-0/upnp/author

urn:schemas-upnp-org:metadata-1-0/upnp/producer

urn:schemas-upnp-org:metadata-1-0/upnp/director

urn:schemas-upnp-org:metadata-1-0/upnp/genre

urn:schemas-upnp-org:metadata-1-0/upnp/album

urn:schemas-upnp-org:metadata-1-0/upnp/playlist

urn:schemas-upnp-org:metadata-1-0/upnp/originalTrackNumber

urn:schemas-upnp-org:metadata-1-0/upnp/userAnnotation

The authority for all of the ‘meta data’ is ‘_:auth42.’ ‘Meta data’statements show that ‘_:auth42’ is ‘Studio Name.’ The authority enablesthe evaluation of both the quality of the file and the ‘meta data’statements associated with the file.

Nodes into a graph are connected via named resource nodes. A statementof ‘meta data’ consist of a subject node, a predicate node and an objectnode. Optionally, an authority node can be connected to the DLG as partof the ‘meta data’ statement.

For each node, there are certain characteristics that help furtherexplain the functionality of the node. The possible types can berepresented as follows using the ANSI C programming language:

/** Invalid Type */ #define RDF_IDENTIFIER_TYPE_UNKNOWN 0x00 /**Resource URI rdf:about */ #define RDF_IDENTIFIER_TYPE_RESOURCE 0x01 /**rdf:NodeId, _:file or generated N-Triples */ #defineRDF_IDENTIFIER_TYPE_ANONYMOUS 0x02 /** Predicate URI */ #defineRDF_IDENTIFIER_TYPE_PREDICATE 0x03 /** rdf:li, rdf:_<n> */ #defineRDF_IDENTIFIER_TYPE_ORDINAL 0x04 /** Authority URI */ #defineRDF_IDENTIFIER_TYPE_AUTHORITY 0x05 /** UTF-8 formatted literal */#define RDF_IDENTIFIER_TYPE_LITERAL 0x06 /** Literal Integer */ #defineRDF_IDENTIFIER_TYPE_INT 0x07 /** Literal XML data */ #defineRDF_IDENTIFIER_TYPE_XML_LITERAL 0x08An example of a data structure (represented in the ANSI C programminglanguage) that represents the ‘meta data’ chunks contained within the‘DXDT’ chunk is as follows:

typedef struct RDFDataStruct {    RDFHeader  Header;    uint32_t numOfStatements;    RDFStatement  statements[RDF_MAX_STATEMENTS]; }RDFData;

The ‘RDFData’ chunk includes a chunk referred to as an ‘RDFHeader’chunk, a value ‘numOfStatements’ and a list of ‘RDFStatement’ chunks.

The ‘RDFHeader’ chunk contains information about the manner in which the‘meta data’ is formatted in the chunk. In one embodiment, the data inthe ‘RDFHeader’ chunk can be represented as follows (represented in ANSIC):

typedef struct RDFHeaderStruct {    uint16_t  versionMajor;    uint16_t versionMinor;    uint16_t  versionFix;    uint16_t  numOfSchemas;   RDFSchema  schemas[RDF_MAX_SCHEMAS]; } RDFHeader;

The ‘RDFHeader’ chunk includes a number ‘version’ that indicates theversion of the resource description format to enable forwardcompatibility. The header includes a second number ‘numOfSchemas’ thatrepresents the number of ‘RDFSchema’ chunks in the list ‘schemas’, whichalso forms part of the ‘RDFHeader’ chunk. In several embodiments, the‘RDFSchema’ chunks are used to enable complex resources to berepresented more efficiently. In one embodiment, the data contained in a‘RDFSchema’ chunk can be represented as follows (represented in ANSI C):

typedef struct RDFSchemaStruct {    wchar_t*   prefix;   wchar_t*   uri; } RDFSchema;

The ‘RDFSchema’ chunk includes a first string of text such as ‘dc’identified as ‘prefix’ and a second string of text such as‘http://purl.org/dc/elements/1.1/’ identified as ‘uri’. The ‘prefix’defines a term that can be used in the ‘meta data’ in place of the‘uri’. The ‘uri’ is a Universal Resource Identifier, which can conformto a specified standardized vocabulary or be a specific vocabulary to aparticular system.

Returning to the discussion of the ‘RDFData’ chunk. In addition to a‘RDFHeader’ chunk, the ‘RDFData’ chunk also includes a value‘numOfStatements’ and a list ‘statement’ of ‘RDFStatement’ chunks. Thevalue ‘numOfStatements’ indicates the actual number of ‘RDFStatement’chunks in the list ‘statements’ that contain information. In oneembodiment, the data contained in the ‘RDFStatement’ chunk can berepresented as follows (represented in ANSI C):

typedef struct RDFStatementStruct {    RDFSubject  subject;   RDFPredicate predicate;    RDFObject  object;    RDFAuthorityauthority; } RDFStatement;

Each ‘RDFStatement’ chunk contains a piece of ‘meta data’ concerning themultimedia file. The chunks ‘subject’, ‘predicate’, ‘object’ and‘authority’ are used to contain the various components of the ‘metadata’ described above.

The ‘subject’ is a ‘RDFSubject’ chunk, which represents the subjectportion of the ‘meta data’ described above. In one embodiment the datacontained within the ‘RDFSubject’ chunk can be represented as follows(represented in ANSI C):

typedef struct RDFSubjectStruct {    uint16_t  type;    wchar_t*  value;} RDFSubject;

The ‘RDFSubject’ chunk shown above includes a value ‘type’ thatindicates that the data is either a Resource or an anonymous node of apiece of ‘meta data’ and a unicode text string ‘value’, which containsdata representing the subject of the piece of ‘meta data’. Inembodiments where an ‘RDFSchema’ chunk has been defined the value can bea defined term instead of a direct reference to a resource.

The ‘predicate’ in a ‘RDFStatement’ chunk is a ‘RDFPredicate’ chunk,which represents the predicate portion of a piece of ‘meta data’. In oneembodiment the data contained within a ‘RDFPredicate’ chunk can berepresented as follows (represented in ANSI C):

typedef struct RDFPredicateStruct {    uint16_t  type;    wchar_t* value; } RDFPredicate;

The ‘RDFPredicate’ chunk shown above includes a value ‘type’ thatindicates that the data is the predicate URI or an ordinal list entry ofa piece of ‘meta data’ and a text string ‘value,’ which contains datarepresenting the predicate of a piece of ‘meta data.’ In embodimentswhere an ‘RDFSchema’ chunk has been defined the value can be a definedterm instead of a direct reference to a resource.

The ‘object’ in a ‘RDFStatement’ chunk is a ‘RDFObject’ chunk, whichrepresents the object portion of a piece of ‘meta data.’ In oneembodiment, the data contained in the ‘RDFObject’ chunk can berepresented as follows (represented in ANSI C):

typedef struct RDFObjectStruct {    uint16_t  type;    wchar_t* language;    wchar_t*  dataTypeURI;    wchar_t*  value; } RDFObject;

The ‘RDFObject’ chunk shown above includes a value ‘type’ that indicatesthat the piece of data is a UTF-8 literal string, a literal integer orliteral XML data of a piece of ‘meta data.’ The chunk also includesthree values. The first value ‘language’ is used to represent thelanguage in which the piece of ‘meta data’ is expressed (e.g. a film'stitle may vary in different languages). In several embodiments, astandard representation can be used to identify the language (such asRFC 3066—Tags for the Identification of Languages specified by theInternet Engineering Task Force, seehttp://www.ietf.org/rfc/rfc3066.txt). The second value ‘dataTypeURI’ isused to indicate the type of data that is contained within the ‘value’field if it can not be explicitly indicated by the ‘type’ field. The URIspecified by the dataTypeURI points to general RDF URI Vocabulary usedto describe the particular type of the Data is used. Different formatsin which the URI can be expressed are described athttp://www.w3.org/TR/rdf-concepts/#section-Datatypes. In one embodiment,the ‘value’ is a ‘wide character.’ In other embodiments, the ‘value’ canbe any of a variety of types of data from a single bit, to an image or avideo sequence. The ‘value’ contains the object piece of the ‘metadata.’

The ‘authority’ in a ‘RDFStatement’ chunk is a ‘RDFAuthority’ chunk,which represents the authority portion of a piece of ‘meta data.’ In oneembodiment the data contained within the ‘RDFAuthority’ chunk can berepresented as follows (represented in ANSI C):

typedef struct RDFAuthorityStruct {    uint16_t  type;    wchar_t* value; } RDFAuthority;

The ‘RDFAuthority’ data structure shown above includes a value ‘type’that indicates the data is a Resource or an anonymous node of a piece of‘meta data.’ The ‘value’ contains the data representing the authorityfor the ‘meta data.’ In embodiments where an ‘RDFSchema’ chunk has beendefined the value can be a defined term instead of a direct reference toa resource.

A conceptual representation of the storage of a ‘DXDT’ chunk of amultimedia file in accordance with an embodiment of the presentinvention is shown in FIG. 2.3. The ‘DXDT’ chunk 38 includes an‘RDFHeader’ chunk 110, a ‘numOfStatements’ value 112 and a list ofRDFStatement chunks 114. The RDFHeader chunk 110 includes a ‘version’value 116, a ‘numOfSchemas’ value 118 and a list of ‘Schema’ chunks 120.Each ‘RDFStatement’ chunk 114 includes a ‘RDFSubject’ chunk 122, a‘RDFPredicate’ chunk 124, a ‘RDFObject’ chunk 126 and a ‘RDFAuthority’chunk 128. The ‘RDFSubject’ chunk includes a ‘type’ value 130 and a‘value’ value 132. The ‘RDFPredicate’ chunk 124 also includes a ‘type’value 134 and a ‘value’ value 136. The ‘RDFObject’ chunk 126 includes a‘type’ value 138, a ‘language’ value 140 (shown in the figure as‘lang’), a ‘dataTypeURI’ value 142 (shown in the figure as ‘dataT’) anda ‘value’ value 144. The ‘RDFAuthority’ chunk 128 includes a ‘type’value 146 and a ‘value’ value 148. Although the illustrated ‘DXDT’ chunkis shown as including a single ‘Schema’ chunk and a single‘RDFStatement’ chunk, one of ordinary skill in the art will readilyappreciate that different numbers of ‘Schema’ chunks and ‘RDFStatement’chunks can be used in a chunk that describes ‘meta data.’

As is discussed below, multimedia files in accordance with embodimentsof the present invention can be continuously modified and updated.Determining in advance the ‘meta data’ to associate with the file itselfand the ‘meta data’ to access remotely (e.g. via the internet) can bedifficult. Typically, sufficient ‘meta data’ is contained within amultimedia file in accordance with an embodiment of the presentinvention in order to describe the contents of the file. Additionalinformation can be obtained if the device reviewing the file is capableof accessing via a network other devices containing ‘meta data’referenced from within the file.

The methods of representing ‘meta data’ described above can beextendable and can provide the ability to add and remove different ‘metadata’ fields stored within the file as the need for it changes overtime. In addition, the representation of ‘meta data’ can be forwardcompatible between revisions.

The structured manner in which ‘meta data’ is represented in accordancewith embodiments of the present invention enables devices to query themultimedia file to better determine its contents. The query could thenbe used to update the contents of the multimedia file, to obtainadditional ‘meta data’ concerning the multimedia file, generate a menurelating to the contents of the file or perform any other functioninvolving the automatic processing of data represented in a standardformat. In addition, defining the length of each parseable element ofthe ‘meta data’ can increase the ease with which devices with limitedamounts of memory, such as consumer electronics devices, can access the‘meta data’.

In other embodiments, the ‘meta data’ is represented using individualchunks for each piece of ‘meta data.’ Several ‘DXDT’ chunks inaccordance with the present invention include a binary chunk containing‘meta data’ encoded as described above and additional chunks containingindividual pieces of ‘meta data’ formatted either as described above orin another format. In embodiments where binary ‘meta data’ is includedin the ‘DXDT’ chunk, the binary ‘meta data’ can be represented using64-bit encoded ASCII. In other embodiments, other binary representationscan be used.

Examples of individual chunks that can be included in the ‘DXDT’ chunkin accordance with the present invention are illustrated in FIG. 2.3.1.The ‘meta data’ includes a ‘MetaData’ chunk 150 that can contain a‘PixelAspectRatioMetaData’ chunk 152 a, an ‘EncoderURIMetaData’ chunk152 b, a ‘CodecSettingsMetaData’ chunk 152 c, a ‘FrameTypeMetaData’chunk 152 d, a ‘VideoResolutionMetaData’ chunk 152 e, a‘PublisherMetaData’ chunk 152 f, a ‘CreatorMetaData’ chunk 152 g, a‘GenreMetaData’ chunk 152 h, a ‘CreatorToolMetaData’ chunk 152 i, a‘RightsMetaData’ chunk 152 j, a ‘RunTimeMetaData’ chunk 152 k, a‘QuantizerMetaData’ chunk 152 l, a ‘CodecInfoMetaData’ chunk 152 m, a‘EncoderNameMetaData’ chunk 152 n, a FrameRateMetaData’ chunk 152 o, a‘InputSourceMetaData’ chunk 152 p, a ‘FileIDMetaData’ chunk 152 q, a‘TypeMetaData’ chunk 152 r, a ‘TitleMetaData’ chunk 152 s and/or a‘CertLevelMetaData’ chunk 152 t.

The ‘PixelAspectRatioMetaData’ chunk 152 a includes informationconcerning the pixel aspect ratio of the encoded video. The‘EncoderURIMetaData’ chunk 152 b includes information concerning theencoder. The ‘CodecSettingsMetaData’ chunk 152 c includes informationconcerning the settings of the codec used to encode the video. The‘FrameTypeMetaData’ chunk 152 d includes information concerning thevideo frames. The ‘VideoResolutionMetaData’ chunk 152 e includesinformation concerning the video resolution of the encoded video. The‘PublisherMetaData’ chunk 152 f includes information concerning theperson or organization that published the media. The ‘CreatorMetaData’chunk 152 g includes information concerning the creator of the content.The ‘GenreMetaData’ chunk 152 h includes information concerning thegenre of the media. The ‘CreatorToolMetaData’ chunk 152 i includesinformation concerning the tool used to create the file. The‘RightsMetaData’ chunk 152 j includes information concerning DRM. The‘RunTimeMetaData’ chunk 152 k includes information concerning the runtime of the media. The ‘QuantizerMetaData’ chunk 152 l includesinformation concerning the quantizer used to encode the video. The‘CodecInfoMetaData’ chunk 152 m includes information concerning thecodec. The ‘EncoderNameMetaData’ chunk 152 n includes informationconcerning the name of the encoder. The FrameRateMetaData’ chunk 152 oincludes information concerning the frame rate of the media. The‘InputSourceMetaData’ chunk 152 p includes information concerning theinput source. The ‘FileIDMetaData’ chunk 152 q includes a uniqueidentifier for the file. The ‘TypeMetaData’ chunk 152 r includesinformation concerning the type of the multimedia file. The‘TitleMetaData’ chunk 152 s includes the title of the media and the‘CertLevelMetaData’ chunk 152 t includes information concerning thecertification level of the media. In other embodiments, additionalchunks can be included that contain additional ‘meta data.’ In severalembodiments, a chunk containing ‘meta data’ in a binary format asdescribed above can be included within the ‘MetaData’ chunk. In oneembodiment, the chunk of binary ‘meta data’ is encoded as 64-bit ASCII.

2.4.1. The ‘Index’ Chunk

In one embodiment, the ‘DXDT’ chunk can include an ‘index’ chunk thatcan be used to index ‘data’ chunks in the ‘movi’ list chunk 42corresponding to specific frames in a sequence of encoded video (the‘movi’ list chunk is discussed further below). The ‘index’ chunk can bedifferentiated from the ‘idx1’ chunk on the basis that the ‘index’ chunkdoes not include information concerning every ‘data’ chunk in the ‘movi’list chunk. Typically, the ‘index’ chunk includes information concerninga subset of the ‘data’ chunks. Appropriate selection of the ‘data’chunks referenced in the ‘index’ chunk can enable rapid location of aspecific video frame.

An embodiment of an ‘index’ chunk in accordance with the presentinvention is shown in FIG. 2.3.2. The ‘index’ chunk 153 includes a listof ‘tag’ chunks 154. In many embodiments, each ‘tag’ chunk 154 containsinformation that can be used to locate a particular encoded frame ofvideo within a multimedia file. In several embodiments, ‘tag’ chunksreference encoded video frames that are approximately evenly spacedthroughout a sequence of encoded video frames. In one embodiment, thelist of ‘tag’ chunks references frames that are spaced at least tenseconds apart. In another embodiments, the ‘tag’ chunks reference framesthat are spaced at least five seconds apart. In a further embodiment,the list of ‘tag’ chunks references frames that are spaced at least onesecond apart. In numerous embodiments, the ‘tag’ chunks reference framesthat are spaced approximately evenly with respect to the bits in themultimedia file or ‘movi’ list chunk. In many embodiments, ‘tag’ chunksare used to identify frames that are the start of specific scenes and/orchapters within a sequence of video frames. In many embodiments, the‘index’ chunk includes a distinct fourcc code such as “idxx”.

In the illustrated embodiment, each ‘tag’ chunk 154 includes informationthat can be used to reference a specific encoded video frame and theportions of one or more audio tracks that accompany the encoded videoframe. The information includes information concerning a chunk offset155 a, information concerning an index offset 155 b, informationidentifying a video frame 155 c and information identifying a portion ofan audio track 155 d.

In many embodiments, the chunk offset 155 a can be used to locate the‘data’ chunks within the multimedia file corresponding to the particularencoded video frame and/or accompanying audio track(s) referenced by the‘tag’ chunk. In one embodiment, the chunk offset is the the location ofthe relevant ‘data’ chunk relative to the start of the ‘movi’ listchunk.

In many embodiments, the index offset 155 b can be used to locateinformation about a particular video frame in the ‘idx1’ chunk. In oneembodiment, the index offset 155 b is the location of the relevant pieceof information relative to the beginning of the ‘idx1’ chunk.

The information identifying the video frame 155 c designates theposition of the encoded video frame referenced by the ‘tag’ chunk withina sequence of encoded video frames. In one embodiment, the information155 c can simply be an integer indicating a frame number in a sequenceof encoded video frames. In other embodiments, other informationindicative of the position of the encoded video frame referenced by the‘tag’ chunk within the video sequence can be used.

In many embodiments, the information identifying a portion of an audiotrack 155 d references a specific section of an audio track. In severalembodiments, the identified section corresponds to the portion of asoundtrack that accompanies the encoded video frame referenced by the‘tag’ chunk. In embodiments where there are multiple audio tracks, theinformation identifying a portion of an audio track 155 d can in factinclude multiple pieces of information capable of referencing sectionswithin each of the multiple audio tracks. In many embodiments, thesections identified by the multiple pieces of information correspond tothe portion of each sound track that accompanies an encoded video framereferenced by the ‘tag’ chunk.

In many embodiments of ‘tag’ chunks in accordance with the presentinvention, various pieces of information are used to identify the ‘data’chunk within a multimedia file corresponding to a specific encoded videoframe. In addition, various types of information can be used to identifyportions of audio and subtitle tracks that accompany an encoded videoframe. In several embodiments, at least some of the ‘tag’ chunks in an‘index’ chunk reference a portion of an audio track and do not referencean encoded video frame.

Including a chunk containing index information before the ‘movi’ listchunk can enable a device to start playing and performing otherfunctions, such as fast forward, rewind and scene skipping, prior to thedownloading of the ‘idx1’ chunk. In one embodiment, the ‘index’ chunk isincluded in a chunk other than the ‘DXDT’ chunk preceding the ‘movi’list chunk (e.g. the junk chunk). In other embodiments, the ‘index’chunk is not located within the ‘junk’ chunk. In several embodiments,the ‘index’ chunk is a separate chunk. In one embodiment, the ‘index’chunk is located after the ‘movi’ list chunk.

2.5. The ‘DMNU’ Chunks

Referring to FIGS. 2.0. and 2.0.1., a first ‘DMNU’ chunk 40 (40′) and asecond ‘DMNU’ chunk 46 (46′) are shown. In FIG. 2.0. the second ‘DMNU’chunk 46 forms part of the multimedia file 30. In the embodimentillustrated in FIG. 2.0.1., the ‘DMNU’ chunk 46′ is contained within aseparate RIFF chunk. In both instances, the first and second ‘DMNU’chunks contain data that can be used to display navigable menus. In oneembodiment, the first ‘DMNU’ chunk 40 (40′) contains data that can beused to create a simple menu that does not include advanced featuressuch as extended background animations. In addition, the second ‘DMNU’chunk 46 (46′) includes data that can be used to create a more complexmenu including such advanced features as an extended animatedbackground.

The ability to provide a so-called ‘lite’ menu can be useful forconsumer electronics devices that cannot process the amounts of datarequired for more sophisticated menu systems. Providing a menu (whether‘lite’ or otherwise) prior to the ‘movi’ list chunk 42 can reduce delayswhen playing embodiments of multimedia files in accordance with thepresent invention in streaming or progressive download applications. Inseveral embodiments, providing a simple and a complex menu can enable adevice to choose the menu that it wishes to display. Placing the smallerof the two menus before the ‘movi’ list chunk 42 enables devices inaccordance with embodiments of the present invention that cannot displaymenus to rapidly skip over information that cannot be displayed.

In other embodiments, the data required to create a single menu is splitbetween the first and second ‘DMNU’ chunks. Alternatively, the ‘DMNU’chunk can be a single chunk before the ‘movi’ chunk containing data fora single set of menus or multiple sets of menus. In other embodiments,the ‘DMNU’ chunk can be a single or multiple chunks located in otherlocations throughout the multimedia file.

In several multimedia files in accordance with the present invention,the first ‘DMNU’ chunk 40 (40′) can be automatically generated based ona ‘richer’ menu in the second ‘DMNU’ chunk 46 (46′). The automaticgeneration of menus is discussed in greater detail below.

The structure of a ‘DMNU’ chunk in accordance with an embodiment of thepresent invention is shown in FIG. 2.4. The ‘DMNU’ chunk 158 is a listchunk that contains a menu chunk 160 and an ‘MRIF’ chunk 162. The menuchunk contains the information necessary to construct and navigatethrough the menus. The ‘MRIF’ chunk contains media information that canbe used to provide subtitles, background video and background audio tothe menus. In several embodiments, the ‘DMNU’ chunk contains menuinformation enabling the display of menus in several differentlanguages.

In one embodiment, the ‘WowMenu’ chunk 160 contains the hierarchy ofmenu chunk objects that are conceptually illustrated in FIG. 2.5. At thetop of the hierarchy is the ‘WowMenuManager’ chunk 170. The‘WowMenuManager’ chunk can contain one or more ‘LanguageMenus’ chunks172 and one ‘Media’ chunk 174.

Use of ‘LanguageMenus’ chunks 172 enables the ‘DMNU’ chunk 158 tocontain menu information in different languages. Each ‘LanguageMenus’chunk 172 contains the information used to generate a complete set ofmenus in a specified language. Therefore, the ‘LanguageMenus’ chunkincludes an identifier that identifies the language of the informationassociated with the ‘LanguageMenus’ chunk. The ‘LanguageMenus’ chunkalso includes a list of ‘WowMenu’ chunks 175.

Each ‘WowMenu’ chunk 175 contains all of the information to be displayedon the screen for a particular menu. This information can includebackground video and audio. The information can also include dataconcerning button actions that can be used to access other menus or toexit the menu and commence displaying a portion of the multimedia file.In one embodiment, the ‘WowMenu’ chunk 175 includes a list of referencesto media. These references refer to information contained in the ‘Media’chunk 174, which will be discussed further below. The references tomedia can define the background video and background audio for a menu.The ‘WowMenu’ chunk 175 also defines an overlay that can be used tohighlight a specific button, when a menu is first accessed.

In addition, each ‘WowMenu’ chunk 175 includes a number of ‘ButtonMenu’chunks 176. Each ‘ButtonMenu’ chunk defines the properties of anonscreen button. The ‘ButtonMenu’ chunk can describe such things as theoverlay to use when the button is highlighted by the user, the name ofthe button and what to do in response to various actions performed by auser navigating through the menu. The responses to actions are definedby referencing an ‘Action’ chunk 178. A single action, e.g. selecting abutton, can result in several ‘Action’ chunks being accessed. Inembodiments where the user is capable of interacting with the menu usinga device such as a mouse that enables an on-screen pointer to movearound the display in an unconstrained manner, the on-screen location ofthe buttons can be defined using a ‘MenuRectangle’ chunk 180. Knowledgeof the on-screen location of the button enables a system to determinewhether a user is selecting a button, when using a free ranging inputdevice.

Each ‘Action’ chunk identifies one or more of a number of differentvarieties of action related chunks, which can include a ‘PlayAction’chunk 182, a ‘MenuTransitionAction’ chunk 184, a ‘ReturnToPlayAction’chunk 186, an ‘AudioSelectAction’ chunk 188, a ‘SubtitileSelectAction’chunk 190 and a ‘ButtonTransitionAction’ chunk 191. A ‘PlayAction’ chunk182 identifies a portion of each of the video, audio and subtitle trackswithin a multimedia file. The ‘PlayAction’ chunk references a portion ofthe video track using a reference to a ‘MediaTrack’ chunk (seediscussion below). The ‘PlayAction’ chunk identifies audio and subtitletracks using ‘SubtitleTrack’ 192 and ‘AudioTrack’ 194 chunks. The‘SubtitleTrack’ and ‘AudioTrack’ chunks both contain references to a‘MediaTrack’ chunk 198. When a ‘PlayAction’ chunk forms the basis of anaction in accordance with embodiments of the present invention, theaudio and subtitle tracks that are selected are determined by the valuesof variables set initially as defaults and then potentially modified bya user's interactions with the menu.

Each ‘MenuTransitionAction’ chunk 184 contains a reference to a‘WowMenu’ chunk 175. This reference can be used to obtain information totransistion to and display another menu.

Each ‘ReturnToPlayAction’ chunk 186 contains information enabling aplayer to return to a portion of the multimedia file that was beingaccessed prior to the user bringing up a menu.

Each ‘AudioSelectAction’ chunk 188 contains information that can be usedto select a particular audio track. In one embodiment, the audio trackis selected from audio tracks contained within a multimedia file inaccordance with an embodiment of the present invention. In otherembodiments, the audio track can be located in an externally referencedfile.

Each ‘SubtitleSelectAction’ chunk 190 contains information that can beused to select a particular subtitle track. In one embodiment, thesubtitle track is selected from a subtitle contained within a multimediafile in accordance with an embodiment of the present invention. In otherembodiments, the subtitle track can be located in an externallyreferenced file.

Each ‘ButtonTransitionAction’ chunk 191 contains information that can beused to transition to another button in the same menu. This is performedafter other actions associated with a button have been performed.

The ‘Media’ chunk 174 includes a number of ‘MediaSource’ chunks 166 and‘MediaTrack’ chunks 198. The ‘Media’ chunk defines all of the multimediatracks (e.g., audio, video, subtitle) used by the feature and the menusystem. Each ‘MediaSource’ chunk 196 identifies a RIFF chunk within themultimedia file in accordance with an embodiment of the presentinvention, which, in turn, can include multiple RIFF chunks. Each‘MediaTrack’ chunk 198 identifies a portion of a multimedia track withina RIFF chunk specified by a ‘MediaSource’ chunk.

The ‘MRIF’ chunk 162 is, essentially, its own small multimedia file thatcomplies with the RIFF format. The ‘MRIF’ chunk contains audio, videoand subtitle tracks that can be used to provide background audio andvideo and overlays for menus. The ‘MRIF’ chunk can also contain video tobe used as overlays to indicate highlighted menu buttons. In embodimentswhere less menu data is required, the background video can be a stillframe (a variation of the AVI format) or a small sequence of identicalframes. In other embodiments, more elaborate sequences of video can beused to provide the background video.

As discussed above, the various chunks that form part of a ‘WowMenu’chunk 175 and the ‘WowMenu’ chunk itself contain references to actualmedia tracks. Each of these references is typically to a media trackdefined in the ‘hdrl’ LIST chunk of a RIFF chunk.

Other chunks that can be used to create a ‘DMNU’ chunk in accordancewith the present invention are shown in FIG. 2.6. The ‘DMNU’ chunkincludes a ‘WowMenuManager’ chunk 170′. The ‘WowMenuManager’ chunk 170′can contain at least one ‘LanguageMenus’ chunk 172′, at least one‘Media’ chunk 174′ and at least one ‘TranslationTable’ chunk 200.

The contents of the ‘LanguageMenus’ chunk 172′ is largely similar tothat of the ‘LanguageMenus’ chunk 172 illustrated in FIG. 2.5. The maindifference is that the ‘PlayAction’ chunk 182′ does not contain‘SubtitleTrack’ chunks 192 and ‘AudioTrack’ chunks 194.

The ‘Media’ chunk 174′ is significantly different from the ‘Media’ chunk174 shown in FIG. 2.5. The ‘Media’ chunk 174′ contains at least one‘Title’ chunk 202 and at least one ‘MenuTracks’ chunk 204. The ‘Title’chunk refers to a title within the multimedia file. As discussed above,multimedia files in accordance with embodiments of the present inventioncan include more than one title (e.g. multiple episodes in a televisionseries, a related series of full length features or simply a selectionof different features). The ‘MenuTracks’ chunk 204 contains informationconcerning media information that is used to create a menu display andthe audio soundtrack and subtitles accompanying the display.

The ‘Title’ chunk can contain at least one ‘Chapter’ chunk 206. The‘Chapter’ chunk 206 references a scene within a particular title. The‘Chapter’ chunk 206 contains references to the portions of the videotrack, each audio track and each subtitle track that correspond to thescene indicated by the ‘Chapter’ chunk. In one embodiment, thereferences are implemented using ‘MediaSource’ chunks 196′ and‘MediaTrack’ chunks 198′ similar to those described above in relation toFIG. 2.5. In several embodiments, a ‘MediaTrack’ chunk references theappropriate portion of the video track and a number of additional‘MediaTrack’ chunks each reference one of the audio tracks or subtitletracks. In one embodiment, all of the audio tracks and subtitle trackscorresponding to a particular video track are referenced using separate‘MediaTrack’ chunks.

As described above, the ‘MenuTracks’ chunks 204 contain references tothe media that are used to generate the audio, video and overlay mediaof the menus. In one embodiment, the references to the media informationare made using ‘MediaSource’ chunks 196′ and ‘MediaTrack’ chunks 198′contained within the ‘MenuTracks’ chunk. In one embodiment, the‘MediaSource’ chunks 196′ and ‘MediaTrack’ chunks 198′ are implementedin the manner described above in relation to FIG. 2.5.

The ‘TranslationTable’ chunk 200 can be used to contain text stringsdescribing each title and chapter in a variety of languages. In oneembodiment, the ‘TranslationTable’ chunk 200 includes at least one‘TranslationLookup’ chunk 208. Each ‘TranslationLookup’ chunk 208 isassociated with a ‘Title’ chunk 202, a ‘Chapter’ chunk 206 or a‘MediaTrack’ chunk 196′ and contains a number of ‘Translation’ chunks210. Each of the ‘Translation’ chunks in a ‘TranslationLookup’ chunkcontains a text string that describes the chunk associated with the‘TranslationLookup’ chunk in a language indicated by the ‘Translation’chunk.

A diagram conceptually illustrating the relationships between thevarious chunks contained within a ‘DMNU’ chunk is illustrated in FIG.2.6.1. The figure shows the containment of one chunk by another chunkusing a solid arrow. The direction in which the arrow points indicatesthe chunk contained by the chunk from which the arrow originates.References by one chunk to another chunk are indicated by a dashed line,where the referenced chunk is indicated by the dashed arrow.

2.6. The ‘Junk’ Chunk

The ‘junk’ chunk 41 is an optional chunk that can be included inmultimedia files in accordance with embodiments of the presentinvention. The nature of the ‘junk’ chunk is specified in the AVI fileformat.

2.7. The ‘Movi’ List Chunk

The ‘movi’ list chunk 42 contains a number of ‘data’ chunks. Examples ofinformation that ‘data’ chunks can contain are audio, video or subtitledata. In one embodiment, the ‘movi’ list chunk includes data for atleast one video track, multiple audio tracks and multiple subtitletracks.

The interleaving of ‘data’ chunks in the ‘movi’ list chunk 42 of amultimedia file containing a video track, three audio tracks and threesubtitle tracks is illustrated in FIG. 2.7. For convenience sake, a‘data’ chunk containing video will be described as a ‘video’ chunk, a‘data’ chunk containing audio will be referred to as an ‘audio’ chunkand a ‘data’ chunk containing subtitles will be referenced as a‘subtitle’ chunk. In the illustrated ‘movi’ list chunk 42, each ‘video’chunk 262 is separated from the next ‘video’ chunk by ‘audio’ chunks 264from each of the audio tracks. In several embodiments, the ‘audio’chunks contain the portion of the audio track corresponding to theportion of video contained in the ‘video’ chunk following the ‘audio’chunk.

Adjacent ‘video’ chunks may also be separated by one or more ‘subtitle’chunks 266 from one of the subtitle tracks. In one embodiment, the‘subtitle’ chunk 266 includes a subtitle and a start time and a stoptime. In several embodiments, the ‘subtitle’ chunk is interleaved in the‘movi’ list chunk such that the ‘video’ chunk following the ‘subtitle’chunk includes the portion of video that occurs at the start time of thesubtitle. In other embodiments, the start time of all ‘subtitle’ and‘audio’ chunks is ahead of the equivalent start time of the video. Inone embodiment, the ‘audio’ and ‘subtitle’ chunks can be placed within 5seconds of the corresponding ‘video’ chunk and in other embodiments the‘audio’ and ‘subtitle’ chunks can be placed within a time related to theamount of video capable of being buffered by a device capable ofdisplaying the audio and video within the file.

In one embodiment, the ‘data’ chunks include a ‘FOURCC’ code to identifythe stream to which the ‘data’ chunk belongs. The ‘FOURCC’ code consistsof a two-digit stream number followed by a two-character code thatdefines the type of information in the chunk. An alternate ‘FOURCC’ codeconsists of a two-character code that defines the type of information inthe chunk followed by the two-digit stream number. Examples of thetwo-character code are shown in the following table:

TABLE 2 Selected two-character codes used in FOURCC codes Two-charactercode Description db Uncompressed video frame dc Compressed video framedd DRM key info for the video frame pc Palette change wb Audio data stSubtitle (text mode) sb Subtitle (bitmap mode) ch Chapter

In one embodiment, the structure of the ‘video’ chunks 262 and ‘audio’chunks 264 complies with the AVI file format. In other embodiments,other formats for the chunks can be used that specify the nature of themedia and contain the encoded media.

In several embodiments, the data contained within a ‘subtitle’ chunk 266can be represented as follows:

typedef struct _subtitlechunk {     FOURCC fcc;     DWORD cb;     STRduration;     STR subtitle; } SUBTITLECHUNK;

The value ‘fcc’ is the FOURCC code that indicates the subtitle track andnature of the subtitle track (text or bitmap mode). The value ‘cb’specifies the size of the structure. The value ‘duration’ specifies thetime at the starting and ending point of the subtitle. In oneembodiment, it can be in the form hh:mm:ss.xxx-hh:mm:ss.xxx. The hhrepresent the hours, mm the minutes, ss the seconds and xxx themilliseconds. The value ‘subtitle’ contains either the Unicode text ofthe subtitle in text mode or a bitmap image of the subtitle in thebitmap mode. Several embodiments of the present invention use compressedbitmap images to represent the subtitle information. In one embodiment,the ‘subtitle’ field contains information concerning the width, heightand onscreen position of the subtitle. In addition, the ‘subtitle’ fieldcan also contain color information and the actual pixels of the bit map.In several embodiments, run length coding is used to reduce the amountof pixel information required to represent the bitmap.

Multimedia files in accordance with embodiments of the present inventioncan include digital rights management. This information can be used invideo on demand applications. Multimedia files that are protected bydigital rights management can only be played back correctly on a playerthat has been granted the specific right of playback. In one embodiment,the fact that a track is protected by digital rights management can beindicated in the information about the track in the ‘hdrl’ list chunk(see description above). A multimedia file in accordance with anembodiment of the present invention that includes a track protected bydigital rights management can also contain information about the digitalrights management in the ‘movi’ list chunk.

A ‘movi’ list chunk of a multimedia file in accordance with anembodiment of the present invention that includes a video track,multiple audio tracks, at least one subtitle track and informationenabling digital rights management is illustrated in FIG. 2.8. The‘movi’ list chunk 42′ is similar to the ‘movi’ list chunk shown in FIG.2.7. with the addition of a ‘DRM’ chunk 270 prior to each video chunk262′. The ‘DRM’ chunks 270 are ‘data’ chunks that contain digital rightsmanagement information, which can be identified by a FOURCC code ‘nndd’.The first two characters ‘nn’ refer to the track number and the secondtwo characters are ‘dd’ to signify that the chunk contains digitalrights management information. In one embodiment, the ‘DRM’ chunk 270provides the digital rights management information for the ‘video’ chunk262′ following the ‘DRM’ chunk. A device attempting to play the digitalrights management protected video track uses the information in the‘DRM’ chunk to decode the video information in the ‘video’ chunk.Typically, the absence of a ‘DRM’ chunk before a ‘video’ chunk isinterpreted as meaning that the ‘video’ chunk is unprotected.

In an encryption system in accordance with an embodiment of the presentinvention, the video chunks are only partially encrypted. Where partialencryption is used, the ‘DRM’ chunks contain a reference to the portionof a ‘video’ chunk that is encrypted and a reference to the key that canbe used to decrypt the encrypted portion. The decryption keys can belocated in a ‘DRM’ header, which is part of the ‘strd’ chunk (seedescription above). The decryption keys are scrambled and encrypted witha master key. The ‘DRM’ header also contains information identifying themaster key.

A conceptual representation of the information in a ‘DRM’ chunk is shownin FIG. 2.9. The ‘DRM’ chunk 270 can include a ‘frame’ value 280, a‘status’ value 282, an ‘offset’ value 284, a ‘number’ value 286 and a‘key’ value 288. The ‘frame’ value can be used to reference theencrypted frame of video. The ‘status’ value can be used to indicatewhether the frame is encrypted, the ‘offset’ value 284 points to thestart of the encrypted block within the frame and the ‘number’ value 286indicates the number of encrypted bytes in the block. The ‘key’ value288 references the decryption key that can be used to decrypt the block.

2.8. The ‘Idx1’ Chunk

The ‘idx1’ chunk 44 is an optional chunk that can be used to index the‘data’ chunks in the ‘movi’ list chunk 42. In one embodiment, the ‘idx1’chunk can be implemented as specified in the AVI format. In otherembodiments, the ‘idx1’ chunk can be implemented using data structuresthat reference the location within the file of each of the ‘data’ chunksin the ‘movi’ list chunk. In several embodiments, the ‘idx1’ chunkidentifies each ‘data’ chunk by the track number of the data and thetype of the data. The FOURCC codes referred to above can be used forthis purpose.

3. Encoding a Multimedia File

Embodiments of the present invention can be used to generate multimediafiles in a number of ways. In one instance, systems in accordance withembodiments of the present invention can generate multimedia files fromfiles containing separate video tracks, audio tracks and subtitletracks. In such instances, other information such as menu informationand ‘meta data’ can be authored and inserted into the file.

Other systems in accordance with embodiments of the present inventioncan be used to extract information from a number of files and author asingle multimedia file in accordance with an embodiment of the presentinvention. Where a CD-R is the initial source of the information,systems in accordance with embodiments of the present invention can usea codec to obtain greater compression and can re-chunk the audio so thatthe audio chunks correspond to the video chunks in the newly createdmultimedia file. In addition, any menu information in the CD-R can beparsed and used to generate menu information included in the multimediafile.

Other embodiments can generate a new multimedia file by addingadditional content to an existing multimedia file in accordance with anembodiment of the present invention. An example of adding additionalcontent would be to add an additional audio track to the file such as anaudio track containing commentary (e.g. director's comments,after-created narrative of a vacation video). The additional audio trackinformation interleaved into the multimedia file could also beaccompanied by a modification of the menu information in the multimediafile to enable the playing of the new audio track.

3.1. Generation Using Stored Data Tracks

A system in accordance with an embodiment of the present invention forgenerating a multimedia file is illustrated in FIG. 3.0. The maincomponent of the system 350 is the interleaver 352. The interleaverreceives chunks of information and interleaves them to create amultimedia file in accordance with an embodiment of the presentinvention in the format described above. The interleaver also receivesinformation concerning ‘meta data’ from a meta data manager 354. Theinterleaver outputs a multimedia file in accordance with embodiments ofthe present invention to a storage device 356.

Typically the chunks provided to the interleaver are stored on a storagedevice. In several embodiments, all of the chunks are stored on the samestorage device. In other embodiments, the chunks may be provided to theinterleaver from a variety of storage devices or generated and providedto the interleaver in real time.

In the embodiment illustrated in FIG. 3.0., the ‘DMNU’ chunk 358 and the‘DXDT’ chunk 360 have already been generated and are stored on storagedevices. The video source 362 is stored on a storage device and isdecoded using a video decoder 364 and then encoded using a video encoder366 to generate a ‘video’ chunk. The audio sources 368 are also storedon storage devices. Audio chunks are generated by decoding the audiosource using an audio decoder 370 and then encoding the decoded audiousing an audio encoder 372. ‘Subtitle’ chunks are generated from textsubtitles 374 stored on a storage device. The subtitles are provided toa first transcoder 376, which converts any of a number of subtitleformats into a raw bitmap format. In one embodiment, the stored subtitleformat can be a format such as SRT, SUB or SSA. In addition, the bitmapformat can be that of a four bit bitmap including a color palettelook-up table. The color palette look-up table includes a 24 bit colordepth identification for each of the sixteen possible four bit colorcodes. A single multimedia file can include more than one color palettelook-up table (see “pc” palette FOURCC code in Table 2 above). The fourbit bitmap thus allows each menu to have 16 different simultaneouscolors taken from a palette of 16 million colors. In alternativeembodiments different numbers of bit per pixel and different colordepths are used. The output of the first transcoder 376 is provided to asecond transcoder 378, which compresses the bitmap. In one embodimentrun length coding is used to compress the bitmap. In other embodiments,other suitable compression formats are used.

In one embodiment, the interfaces between the various encoders, decoderand transcoders conform with Direct Show standards specified byMicrosoft Corporation. In other embodiments, the software used toperform the encoding, decoding and transcoding need not comply with suchstandards.

In the illustrated embodiment, separate processing components are shownfor each media source. In other embodiments resources can be shared. Forexample, a single audio decoder and audio encoder could be used togenerate audio chunks from all of the sources. Typically, the entiresystem can be implemented on a computer using software and connected toa storage device such as a hard disk drive.

In order to utilize the interleaver in the manner described above, the‘DMNU’ chunk, the ‘DXDT’ chunk, the ‘video’ chunks, the ‘audio’ chunksand the ‘subtitle’ chunks in accordance with embodiments of the presentinvention must be generated and provided to the interleaver. The processof generating each of the various chunks in a multimedia file inaccordance with an embodiment of the present invention is discussed ingreater detail below.

3.2. Generating a ‘DXDT’ Chunk

The ‘DXDT’ chunk can be generated in any of a number of ways. In oneembodiment, ‘meta data’ is entered into data structures via a graphicaluser interface and then parsed into a ‘DXDT’ chunk. In one embodiment,the ‘meta data’ is expressed as series of subject, predicate, object andauthority statements. In another embodiment, the ‘meta data’ statementsare expressed in any of a variety of formats. In several embodiments,each ‘meta data’ statement is parsed into a separate chunk. In otherembodiments, several ‘meta data’ statements in a first format (such assubject, predicate, object, authority expressions) are parsed into afirst chunk and other ‘meta data’ statements in other formats are parsedinto separate chunks. In one embodiment, the ‘meta data’ statements arewritten into an XML configuration file and the XML configuration file isparsed to create the chunks within a ‘DXDT’ chunk.

An embodiment of a system for generating a ‘DXDT’ chunk from a series of‘meta data’ statements contained within an XML configuration file isshown in FIG. 3.1. The system 380 includes an XML configuration file382, which can be provided to a parser 384. The XML configuration fileincludes the ‘meta data’ encoded as XML. The parser parses the XML andgenerates a ‘DXDT’ chunk 386 by converting the ‘meta data’ statementinto chunks that are written to the ‘DXDT’ chunk in accordance with anyof the ‘meta data’ chunk formats described above.

3.3.1. Generating an ‘Index’ Chunk

As discussed above, many embodiments of ‘DXDT’ chunks in accordance withthe present invention can include an ‘index’ chunk. An ‘index’ chunk canbe automatically generated following the completion of the encoding ofthe audio, video and/or subtitle tracks contained within a multimediafile. In one embodiment, an ‘index’ chunk is generated by referencingencoded video frames and any accompanying audio at approximately evenlyspaced intervals within an encoded video track. In other embodiments,video frames associated with scenes and/or chapters within an encodedvideo track can be identified and used to automatically generate an‘index’ chunk. In many embodiments, ‘index’ chunks can be generatedmanually, generated automatically using menu information or generatedusing any number of algorithms appropriate to the sequence of videoindexed by the ‘index’ chunk.

3.3. Generating a ‘DMNU’ Chunk

A system that can be used to generate a ‘DMNU’ chunk in accordance withan embodiment of the present invention is illustrated in FIG. 3.2. Themenu chunk generating system 420 requires as input a media model 422 andmedia information. The media information can take the form of a videosource 424, an audio source 426 and an overlay source 428.

The generation of a ‘DMNU’ chunk using the inputs to the menu chunkgenerating system involves the creation of a number of intermediatefiles. The media model 422 is used to create an XML configuration file430 and the media information is used to create a number of AVI files432. The XML configuration file is created by a model transcoder 434.The AVI files 432 are created by interleaving the video, audio andoverlay information using an interleaver 436. The video information isobtained by using a video decoder 438 and a video encoder 440 to decodethe video source 424 and recode it in the manner discussed below. Theaudio information is obtained by using an audio decoder 442 and an audioencoder 444 to decode the audio and encode it in the manner describedbelow. The overlay information is generated using a first transcoder 446and a second transcoder 448. The first transcoder 446 converts theoverlay into a graphical representation such as a standard bitmap andthe second transcoder takes the graphical information and formats it asis required for inclusion in the multimedia file. Once the XML file andthe AVI files containing the information required to build the menushave been generated, the menu generator 450 can use the information togenerate a ‘DMNU’ chunk 358′.

3.3.1. The Menu Model

In one embodiment, the media model is an object-oriented modelrepresenting all of the menus and their subcomponents. The media modelorganizes the menus into a hierarchical structure, which allows themenus to be organized by language selection. A media model in accordancewith an embodiment of the present invention is illustrated in FIG. 3.3.The media model 460 includes a top-level ‘MediaManager’ object 462,which is associated with a number of ‘LanguageMenus’ objects 463, a‘Media’ object 464 and a ‘TranslationTable’ object 465. The ‘MenuManager’ also contains the default menu language. In one embodiment, thedefault language can be indicated by ISO 639 two-letter language code.

The ‘LanguageMenus’ objects organize information for various menus bylanguage selection. All of the ‘Menu’ objects 466 for a given languageare associated with the ‘LanguageMenus’ object 463 for that language.Each ‘Menu’ object is associated with a number of ‘Button’ objects 468and references a number of ‘MediaTrack’ objects 488. The referenced‘MediaTrack’ objects 488 indicated the background video and backgroundaudio for the ‘Menu’ object 466.

Each ‘Button’ object 468 is associated with an ‘Action’ object 470 and a‘Rectangle’ object 484. The ‘Button’ object 468 also contains areference to a ‘MediaTrack’ object 488 that indicates the overlay to beused when the button is highlighted on a display. Each ‘Action’ object470 is associated with a number of objects that can include a‘MenuTransition’ object 472, a ‘ButtonTransition’ object 474, a‘ReturnToPlay’ object 476, a ‘Subtitle Selection’ object 478, an‘AudioSelection’ object 480 and a ‘PlayAction’ object 482. Each of theseobjects define the response of the menu system to various inputs from auser. The ‘MenuTransition’ object contains a reference to a ‘Menu’object that indicates a menu that should be transitioned to in responseto an action. The ‘ButtonTransition’ object indicates a button thatshould be highlighted in response to an action. The ‘ReturnToPlay’object can cause a player to resume playing a feature. The‘SubtitleSelection’ and ‘AudioSelection’ objects contain references to‘Title’ objects 487 (discussed below). The ‘PlayAction’ object containsa reference to a ‘Chapter’ object 492 (discussed below). The ‘Rectangle’object 484 indicates the portion of the screen occupied by the button.

The ‘Media’ object 464 indicates the media information referenced in themenu system. The ‘Media’ object has a ‘MenuTracks’ object 486 and anumber of ‘Title’ objects 487 associated with it. The ‘MenuTracks’object 486 references ‘MediaTrack’ objects 488 that are indicative ofthe media used to construct the menus (i.e. background audio, backgroundvideo and overlays).

The ‘Title’ objects 487 are indicative of a multimedia presentation andhave a number of ‘Chapter’ objects 492 and ‘MediaSource’ objects 490associated with them. The ‘Title’ objects also contain a reference to a‘TranslationLookup’ object 494. The ‘Chapter’ objects are indicative ofa certain point in a multimedia presentation and have a number of‘MediaTrack’ objects 488 associated with them. The ‘Chapter’ objectsalso contain a reference a ‘TranslationLookup’ object 494. Each‘MediaTrack’ object associated with a ‘Chapter’ object is indicative ofa point in either an audio, video or subtitle track of the multimediapresentation and references a ‘MediaSource’ object 490 and a‘TransalationLookup’ object 494 (discussed below).

The ‘TranslationTable’ object 465 groups a number of text strings thatdescribe the various parts of multimedia presentations indicated by the‘Title’ objects, the ‘Chapter’ objects and the ‘MediaTrack’ objects. The‘TranslationTable’ object 465 has a number of ‘TranslationLookup’objects 494 associated with it. Each ‘TranslationLookup’ object isindicative of a particular object and has a number of ‘Translation’objects 496 associated with it. The ‘Translation’ objects are eachindicative of a text string that describes the object indicated by the‘TranslationLookup’ object in a particular language.

A media object model can be constructed using software configured togenerate the various objects described above and to establish therequired associations and references between the objects.

3.3.2. Generating an XML File

An XML configuration file is generated from the menu model, whichrepresents all of the menus and their sub-components. The XMLconfiguration file also identifies all the media files used by themenus. The XML can be generated by implementing an appropriate parserapplication that parses the object model into XML code.

In other embodiments, a video editing application can provide a userwith a user interface enabling the direct generation of an XMLconfiguration file without creating a menu model.

In embodiments where another menu system is the basis of the menu model,such as a DVD menu, the menus can be pruned by the user to eliminatemenu options relating to content not included in the multimedia filegenerated in accordance with the practice of the present invention. Inone embodiment, this can be done by providing a graphical user interfaceenabling the elimination of objects from the menu model. In anotherembodiment, the pruning of menus can be achieved by providing agraphical user interface or a text interface that can edit the XMLconfiguration file.

3.3.3. The Media Information

When the ‘DMNU’ chunk is generated, the media information provided tothe menu generator 450 includes the data required to provide thebackground video, background audio and foreground overlays for thebuttons specified in the menu model (see description above). In oneembodiment, a video editing application such as VideoWave distributed byRoxio, Inc. of Santa Clara, Calif. is used to provide the source mediatracks that represent the video, audio and button selection overlays foreach individual menu.

3.3.4. Generating Intermediate AVI Files

As discussed above, the media tracks that are used as the backgroundvideo, background audio and foreground button overlays are stored in asingle AVI file for one or more menus. The chunks that contain the mediatracks in a menu AVI file can be created by using software designed tointerleave video, audio and button overlay tracks. The ‘audio’, ‘video’and ‘overlay’ chunks (i.e. ‘subtitle’ chunks containing overlayinformation) are interleaved into an AVI format compliant file using aninterleaver.

As mentioned above, a separate AVI file can be created for each menu. Inother embodiments, other file formats or a single file could be used tocontain the media information used to provide the background audio,background video and foreground overlay information.

3.3.5. Combining the XML Configuration File and the AVI Files

In one embodiment, a computer is configured to parse information fromthe XML configuration file to create a ‘WowMenu’ chunk (describedabove). In addition, the computer can create the ‘MRIF’ chunk (describedabove) using the AVI files that contain the media for each menu. Thecomputer can then complete the generation of the ‘DMNU’ chunk bycreating the necessary references between the ‘WowMenu’ chunk and themedia chunks in the ‘MIF’ chunk. In several embodiments, the menuinformation can be encrypted. Encryption can be achieved by encryptingthe media information contained in the ‘MRIF’ chunk in a similar mannerto that described below in relation to ‘video’ chunks. In otherembodiments, various alternative encryption techniques are used.

3.3.6. Automatic Generation of Menus from the Object Model

Referring back to FIG. 3.3., a menu that contains less content than thefull menu can be automatically generated from the menu model by simplyexamining the ‘Title’ objects 487 associated with the ‘Media object 464.The objects used to automatically generate a menu in accordance with anembodiment of the invention are shown in FIG. 3.3.1. Software cangenerate an XML configuration file for a simple menu that enablesselection of a particular section of a multimedia presentation andselection of the audio and subtitle tracks to use. Such a menu can beused as a first so-called ‘lite’ menu in several embodiments ofmultimedia files in accordance with the present invention.

3.3.7. Generating ‘DXDT’ and ‘DMNU’ Chunks Using a Single ConfigurationFile

Systems in accordance with several embodiments of the present inventionare capable of generating a single XML configuration file containingboth ‘meta data’ and menu information and using the XML file to generatethe ‘DXDT’ and ‘DMNU’ chunks. These systems derive the XML configurationfile using the ‘meta data’ information and the menu object model. Inother embodiments, the configuration file need not be in XML.

3.4. Generating ‘Audio’ Chunks

The ‘audio’ chunks in the ‘movi’ list chunk of multimedia files inaccordance with embodiments of the present invention can be generated bydecoding an audio source and then encoding the source into ‘audio’chunks in accordance with the practice of the present invention. In oneembodiment, the ‘audio’ chunks can be encoded using an mp3 codec.

3.4.1. Re-chunking Audio

Where the audio source is provided in chunks that don't contain audioinformation corresponding to the contents of a corresponding ‘video’chunk, then embodiments of the present invention can re-chunk the audio.A process that can be used to re-chunk audio is illustrated in FIG. 3.4.The process 480 involves identifying (482) a ‘video’ chunk, identifying(484) the audio information that accompanies the ‘video’ chunk andextracting (486) the audio information from the existing audio chunks tocreate (488) a new ‘audio’ chunk. The process is repeated until thedecision (490) is made that the entire audio source has been re-chunked.At which point, the rechunking of the audio is complete (492).

3.5. Generating ‘Video’ Chunks

As described above the process of creating video chunks can involvedecoding the video source and encoding the decoded video into ‘video’chunks. In one embodiment, each ‘video’ chunk contains information for asingle frame of video. The decoding process simply involves taking videoin a particular format and decoding the video from that format into astandard video format, which may be uncompressed. The encoding processinvolves taking the standard video, encoding the video and generating‘video’ chunks using the encoded video.

A video encoder in accordance with an embodiment of the presentinvention is conceptually illustrated in FIG. 3.5. The video encoder 500preprocesses 502 the standard video information 504. Motion estimation506 is then performed on the preprocessed video to provide motioncompensation 508 to the preprocessed video. A discrete cosine transform(DCT transformation) 510 is performed on the motion compensated video.Following the DCT transformation, the video is quantized 512 andprediction 514 is performed. A compressed bitstream 516 is thengenerated by combining a texture coded 518 version of the video withmotion coding 520 generated using the results of the motion estimation.The compressed bitstream is then used to generate the ‘video’ chunks.

In order to perform motion estimation 506, the system must haveknowledge of how the previously processed frame of video will be decodedby a decoding device (e.g. when the compressed video is uncompressed forviewing by a player). This information can be obtained by inversequantizing 522 the output of the quantizer 512. An inverse DCT 524 canthen be performed on the output of the inverse quantizer and the resultplaced in a frame store 526 for access during the motion estimationprocess.

Multimedia files in accordance with embodiments of the present inventioncan also include a number of psychovisual enhancements 528. Thepsychovisual enhancements can be methods of compressing video based uponhuman perceptions of vision. These techniques are discussed furtherbelow and generally involve modifying the number of bits used by thequantizer to represent various aspects of video. Other aspects of theencoding process can also include psychovisual enhancements.

In one embodiment, the entire encoding system 500 can be implementedusing a computer configured to perform the various functions describedabove. Examples of detailed implementations of these functions areprovided below.

3.5.1. Preprocessing

The preprocessing operations 502 that are optionally performed by anencoder 500 in accordance with an embodiment of the present inventioncan use a number of signal processing techniques to improve the qualityof the encoded video. In one embodiment, the preprocessing 502 caninvolve one or all of deinterlacing, temporal/spatial noise reductionand resizing. In embodiments where all three of these preprocessingtechniques are used, the deinterlacing is typically performed firstfollowed by the temporal/spatial noise reduction and the resizing.

3.5.2. Motion Estimation and Compensation

A video encoder in accordance with an embodiment of the presentinvention can reduce the number of pixels required to represent a videotrack by searching for pixels that are repeated in multiple frames.Essentially, each frame in a video typically contains many of the samepixels as the one before it. The encoder can conduct several types ofsearches for matches in pixels between each frame (as macroblocks,pixels, half-pixels and quarter-pixels) and eliminates theseredundancies whenever possible without reducing image quality. Usingmotion estimation, the encoder can represent most of the picture simplyby recording the changes that have occurred since the last frame insteadof storing the entire picture for every frame. During motion estimation,the encoder divides the frame it is analyzing into an even grid ofblocks, often referred to as ‘macroblocks’. For each ‘macroblock’ in theframe, the encoder can try to find a matching block in the previousframe. The process of trying to find matching blocks is called a ‘motionsearch’. The motion of the ‘macroblock’ can be represented as a twodimensional vector, i.e. an (x,y) representation. The motion searchalgorithm can be performed with various degrees of accuracy. A whole-pelsearch is one where the encoder will try to locate matching blocks bystepping through the reference frame in either dimension one pixel at atime. In a half-pixel search, the encoder searches for a matching blockby stepping through the reference frame in either dimension by half of apixel at a time. The encoder can use quarter-pixels, other pixelfractions or searches involving a granularity of greater than a pixel.

The encoder embodiment illustrated in FIG. 3.5. performs motionestimation in accordance with an embodiment of the present invention.During motion estimation the encoder has access to the preprocessedvideo 502 and the previous frame, which is stored in a frame store 526.The previous frame is generated by taking the output of the quantizer,performing an inverse quantization 522 and an inverse DCT transformation524. The reason for performing the inverse functions is so that theframe in the frame store is as it will appear when decoded by a playerin accordance with an embodiment of the present invention.

Motion compensation is performed by taking the blocks and vectorsgenerated as a result of motion estimation. The result is anapproximation of the encoded image that can be matched to the actualimage by providing additional texture information.

3.5.3. Discrete Cosine Transform

The DCT and inverse DCT performed by the encoder illustrated in FIG.3.5. are in accordance with the standard specified in ISO/IEC14496-2:2001(E), Annex A.1 (coding transforms).

-   -   3.5.3.1. Description of Transform

The DCT is a method of transforming a set of spatial-domain data pointsto a frequency domain representation. In the case of video compression,a 2-dimensional DCT converts image blocks into a form where redundanciesare more readily exploitable. A frequency domain block can be a sparsematrix that is easily compressed by entropy coding.

-   -   3.5.3.2. Psychovisual Enhancements to Transform

The DCT coefficients can be modified to improve the quality of thequantized image by reducing quantization noise in areas where it isreadily apparent to a human viewer. In addition, file size can bereduced by increasing quantization noise in portions of the image whereit is not readily discernable by a human viewer.

Encoders in accordance with an embodiment of the present invention canperform what is referred to as a ‘slow’ psychovisual enhancement. The‘slow’ psychovisual enhancement analyzes blocks of the video image anddecides whether allowing some noise there can save some bits withoutdegrading the video's appearance. The process uses one metric per block.The process is referred to as a ‘slow’ process, because it performs aconsiderable amount of computation to avoid blocking or ringingartifacts.

Other embodiments of encoders in accordance with embodiments of thepresent invention implement a ‘fast’ psychovisual enhancement. The‘fast’ psychovisual enhancement is capable of controlling where noiseappears within a block and can shape quantization noise.

Both the ‘slow’ and ‘fast’ psychovisual enhancements are discussed ingreater detail below. Other psychovisual enhancements can be performedin accordance with embodiments of the present invention includingenhancements that control noise at image edges and that seek toconcentrate higher levels of quantization noise in areas of the imagewhere it is not readily apparent to human vision.

-   -   3.5.3.3. ‘Slow’ Psychovisual Enhancement

The ‘slow’ psychovisual enhancement analyzes blocks of the video imageand determines whether allowing some noise can save bits withoutdegrading the video's appearance. In one embodiment, the algorithmincludes two stages. The first involves generation of a differentiatedimage for the input luminance pixels. The differentiated image isgenerated in the manner described below. The second stage involvesmodifying the DCT coefficients prior to quantization.

-   -   3.5.3.3.1. Generation of Differentiated Image

Each pixel p′_(xy) of the differentiated image is computed from theuncompressed source pixels, p_(xy), according to the following:p′ _(xy)=max(|p _(x+1y) −p _(xy) |,|p _(x−1y) −p _(xy) |,|p _(xy+1) −p_(xy) |,|p _(xy−1) −p _(xy)|)

where

p′_(xy) will be in the range 0 to 255 (assuming 8 bit video).

-   -   3.5.3.3.2. Modification of DCT Coefficients

The modification of the DCT coefficients can involve computation of ablock ringing factor, computation of block energy and the actualmodification of the coefficient values.

-   -   3.5.3.3.3. Computation of Block Ringing Factor

For each block of the image, a “ringing factor” is calculated based onthe local region of the differentiated image. In embodiments where theblock is defined as an 8×8 block, the ringing factor can be determinedusing the following method.

Initially, a threshold is determined based on the maximum and minimumluminance pixels values within the 8×8 block:threshold_(block)=floor((max_(block)−min_(block))/8)+2

The differentiated image and the threshold are used to generate a map ofthe “flat” pixels in the block's neighborhood. The potential for eachblock to have a different threshold prevents the creation of a map offlat pixels for the entire frame. The map is generated as follows:flat_(xy)=1 when p′ _(xy)<threshold_(block)flat_(xy)=0 otherwise

The map of flat pixels is filtered according to a simple logicaloperation:flat′_(xy)=1 when flat_(xy)=1 and flat_(x−1y)=1 and flat_(xy−1)=1 andflat_(x−1y−1)=1flat′_(xy) otherwise

The flat pixels in the filtered map are then counted over the 9×9 regionthat covers the 8×8 block.flatcount_(block)=Σflat′_(xy) for 0=x=8 and 0=y=8

The risk of visible ringing artifacts can be evaluated using thefollowing expression:ringingbrisk_(block)=((flatcount_(block)−10)×256+20)/40

The 8×8 block's ringing factor can then be derived using the followingexpression:Ringingfactor=0 when ringingrisk>255=255 when ringingrisk<0=255−ringingrisk otherwis

3.5.3.3.4. Computation of Block Energy

The energy for blocks of the image can be calculated using the followingprocedure. In several embodiments, 8×8 blocks of the image are used.

A forward DCT is performed on the source image:T=ƒDCT(S)

where S is the 64 source-image luminance values of the 8×8 block inquestion and T is the transformed version of the same portion of thesource image.

The energy at a particular coefficient position is defined as the squareof that coefficient's value:e_(k)=t_(k) ² for 0=k=63

where t_(k) is the kth coefficient of transformed block T.

-   -   3.5.3.3.5. Coefficient Modification

The modification of the DCT coefficients can be performed in accordancewith the following process. In several embodiments, the process isperformed for every non-zero AC DCT coefficient before quantization. Themagnitude of each coefficient is changed by a small delta, the value ofthe delta being determined according to psychovisual techniques.

The DCT coefficient modification of each non-zero AC coefficient c_(k)is performed by calculating an energy based on local and block energiesusing the following formula:energy_(k)=max(a _(k) ×e _(k),0.12×totalenergy)

where a_(k) is a constant whose value depends on the coefficientposition as described in the following table:

TABLE 3 Coefficient table 0.0 1.0 1.5 2.0 2.0 2.0 2.0 2.0 1.0 1.5 2.02.0 2.0 2.0 2.0 2.0 1.5 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.02.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.02.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0

The energy can be modified according to the block's ringing factor usingthe following relationship:energy′_(k)=ringingfactor×energy_(k)

The resulting value is shifted and clipped before being used as an inputto a look-up table (LUT).e _(k)=min(1023,4×energy′_(k))d_(k)=LUT_(i) where i=e_(k)

The look-up table is computed as follows:LUT_(i)=min(floor(k _(texture)×((i+0.5)/4)^(½) +k _(flat)×offset),2×Q_(p))

TABLE 4 offset as a function of Q_(p) values The value ‘offset’ dependson quantizer, Q_(p), as described in the following table: Q_(p) offset 1−0.5 2 1.5 3 1.0 4 2.5 5 1.5 6 3.5 7 2.5 8 4.5 9 3.5 10 5.5 11 4.5 126.5 13 5.5 14 7.5 15 6.5 16 8.5 17 7.5 18 9.5 19 8.5 20 10.5 21 9.5 2211.5 23 10.5 24 12.5 25 11.5 26 13.5 27 12.5 28 14.5 29 13.5 30 15.5 3114.5

The variable k_(texture) and k_(flat) control the strength of the of thepsychovisual effect in flat and textured regions respectively. In oneembodiment, they take values in the range 0 to 1, with 0 signifying noeffect and 1 meaning full effect. In one embodiment, the values fork_(texture) and k_(flat) are established as follows:

Luminance:k_(texture)=1.0k_(flat)=1.0

Chrominance:k_(texture)=1.0k_(flat)=0.0

The output from the look-up table (d_(k)) is used to modify themagnitude of the DCT coefficient by an additive process:c′ _(k) =c _(k)−min(d _(k) ,|c _(k)|)×sgn(c _(k))

Finally, the DCT coefficient c_(k) is substituted by the modifiedcoefficient c′_(k) and passed onwards for quantization.

3.5.3.4. ‘Fast’ Psychovisual Enhancement

A ‘fast’ psychovisual enhancement can be performed on the DCTcoefficients by computing an ‘importance’ map for the input luminancepixels and then modifying the DCT coefficients.

-   -   3.5.3.4.1. Computing an ‘Importance’ Map

An ‘importance’ map can be generated by calculating an ‘importance’value for each pixel in the luminance place of the input video frame. Inseveral embodiments, the ‘importance’ value approximates the sensitivityof the human eye to any distortion located at that particular pixel. The‘importance’ map is an array of pixel ‘importance’ values.

The ‘importance’ of a pixel can be determined by first calculating thedynamic range of a block of pixels surrounding the pixel (d_(xy)). Inseveral embodiments the dynamic range of a 3×3 block of pixels centeredon the pixel location (x, y) is computed by subtracting the value of thedarkest pixel in the area from the value of the lightest pixel in thearea.

The ‘importance’ of a pixel (m_(xy)) can be derived from the pixel'sdynamic range as follows:m _(xy)=0.08/max(d _(xy),3)+0.001

-   -   3.5.3.4.2. Modifying DCT Coefficients

In one embodiment, the modification of the DCT coefficients involves thegeneration of basis-function energy matrices and delta look up tables.

-   -   3.5.3.4.3. Generation of Basis-function Energy Matrices

A set of basis-function energy matrices can be used in modifying the DCTcoefficients. These matrices contain constant values that may becomputed prior to encoding. An 8×8 matrix is used for each of the 64 DCTbasis functions. Each matrix describes how every pixel in an 8×8 blockwill be impacted by modification of its corresponding coefficient. Thekth basis-function energy matrix is derived by taking an 8×8 matrixA_(k) with the corresponding coefficient set to 100 and the othercoefficients set to 0.

$\begin{matrix}{a_{kn} = 100} & {{{if}\mspace{14mu} n} = k} \\{= 0} & {otherwise}\end{matrix}$

where

n represents the coefficient position within the 8×8 matrix; 0=n=63

An inverse DCT is performed on the matrix to yield a further 8×8 matrixA′_(k). The elements of the matrix (a′_(kn)) represent the kth DCT basisfunction.A′ _(k) =iDCT(A _(k))

Each value in the transformed matrix is then squared:b_(kn)=a′_(kn) ² for 0=n=63

The process is carried out 64 times to produce the basis function energymatrices B_(k), 0=k=63, each comprising 64 natural values. Each matrixvalue is a measure of how much a pixel at the nth position in the 8×8block will be impacted by any error or modification of the coefficientk.

-   -   3.5.3.4.4. Generation of Delta Look-up Table

A look-up table (LUT) can be used to expedite the computation of thecoefficient modification delta. The contents of the table can begenerated in a manner that is dependent upon the desired strength of the‘fast’ psychovisual enhancement and the quantizer parameter (Q_(p)).

The values of the look-up table can be generated according to thefollowing relationship:LUT_(i)=min(floor(128×k _(texture)×strength/(i+0.5)+k_(flat)×offset+0.5),2×Q _(p))

where

i is the position within the table, 0=i=1023.

strength and offset depend on the quantizer, Q_(p), as described in thefollowing table:

TABLE 5 Relationship between values of strength and offset and the valueof Q_(p) Q_(p) strength offset 1 0.2 −0.5 2 0.6 1.5 3 1.0 1.0 4 1.2 2.55 1.3 1.5 6 1.4 3.5 7 1.6 2.5 8 1.8 4.5 9 2.0 3.5 10 2.0 5.5 11 2.0 4.512 2.0 6.5 13 2.0 5.5 14 2.0 7.5 15 2.0 6.5 16 2.0 8.5 17 2.0 7.5 18 2.09.5 19 2.0 8.5 20 2.0 10.5 21 2.0 9.5 22 2.0 11.5 23 2.0 10.5 24 2.012.5 25 2.0 11.5 26 2.0 13.5 27 2.0 12.5 28 2.0 14.5 29 2.0 13.5 30 2.015.5 31 2.0 14.5

The variable k_(texture) and k_(flat) control the strength of the of thepsychovisual effect in flat and textured regions respectively. In oneembodiment, they take values in the range 0 to 1, with 0 signifying noeffect and 1 meaning full effect. In one embodiment, the values fork_(texture) and k_(flat) are established as follows:

Luminance:k_(texture)=1.0k_(flat)=1.0

Chrominance:k_(texture)=1.0k_(flat)=0.0

-   -   3.5.3.4.5. Modification of DCT Coefficients

The DCT coefficients can be modified using the values calculated above.In one embodiment, each non-zero AC DCT coefficient is modified inaccordance with the following procedure prior to quantization.

Initially, an ‘energy’ value (e_(k)) is computed by taking the dotproduct of the corresponding basis function energy matrix and theappropriate 8×8 block from the importance map. This ‘energy’ is ameasure of how quantization errors at the particular coefficient wouldbe perceived by a human viewer. It is the sum of the product of pixelimportance and pixel basis-function energy:e _(k) =M·B _(k)

where

M contains the 8×8 block's importance map values; and

B_(k) is the kth basis function energy matrix.

The resulting ‘energy’ value is shifted and clipped before being used asan index (d_(k)) into the delta look-up table.e′ _(k)=min[1023,floor(e _(k)/32768)]d_(k)=LUT_(i)

wherei=e′_(k)

The output of the delta look-up table is used to modify the magnitude ofthe DCT coefficient by an additive process:c′ _(k) =c _(k)−min(d _(k) ,|c _(k)|)×sign(c _(k))

The DCT coefficient c_(k) is substituted with the modified c′_(k) andpassed onwards for quantization.

3.5.4. Quantization

Encoders in accordance with embodiments of the present invention can usea standard quantizer such as a the quantizer defined by theInternational Telecommunication Union as Video Coding for Low BitrateCommunication, ITU-T Recommendation H.263, 1996.

-   -   3.5.4.1. Psychovisual Enhancements to Quantization

Some encoders in accordance with embodiments of the present invention,use a psychovisual enhancement that exploits the psychological effectsof human vision to achieve more efficient compression. The psychovisualeffect can be applied at a frame level and a macroblock level.

-   -   3.5.4.2. Frame Level Psychovisual Enhancements

When applied at a frame level, the enhancement is part of the ratecontrol algorithm and its goal is to adjust the encoding so that a givenamount of bit rate is best used to ensure the maximum visual quality asperceived by human eyes. The frame rate psychovisual enhancement ismotivated by the theory that human vision tends to ignore the detailswhen the action is high and that human vision tends to notice detailwhen an image is static. In one embodiment, the amount of motion isdetermined by looking at the sum of absolute difference (SAD) for aframe. In one embodiment, the SAD value is determined by summing theabsolute differences of collocated luminance pixels of two blocks. Inseveral embodiments, the absolute differences of 16×16 pixel blocks isused. In embodiments that deal with fractional pixel offsets,interpolation is performed as specified in the MPEG-4 standard (anISO/IEC standard developed by the Moving Picture Experts Group of theISO/IEC), before the sum of absolute differences is calculated.

The frame-level psychovisual enhancement applies only to the P frames ofthe video track and is based on SAD value of the frame. During theencoding, the psychovisual module keeps a record of the average SAD(i.e. SAD) of all of the P frames of the video track and the averagedistance of the SAD of each frame from its overall SAD (i.e. DSAD). Theaveraging can be done using an exponential moving average algorithm. Inone embodiment, the one-pass rate control algorithm described above canbe used as the averaging period here (see description above).

For each P frame of the video track encoded, the frame quantizer Q(obtained from the rate control module) will have a psychovisualcorrection applied to it. In one embodiment, the process involvescalculating a ratio R using the following formula:

$R = {\frac{{SAD} - \overset{\_}{SAD}}{\overset{\_}{DSAD}} - I}$

where

I is a constant and is currently set to 0.5. The R is clipped to withinthe bound of [−1, 1].

The quantizer is then adjusted according to the ration R, via thecalculation shown below:Q _(adj) =Q└Q.(1+R.S _(frame))┘

where

S_(frame) is a strength constant for the frame level psychovisualenhancements.

The S_(frame) constant determines how strong an adjustment can be forthe frame level psychovisual. In one embodiment of the codec, the optionof setting S_(frame) to 0.2, 0.3 or 0.4 is available.

-   -   3.5.4.3. Macroblock Level Psychovisual Enhancements

Encoders in accordance with embodiments of the present invention thatutilize a psychovisual enhancement at the macroblock level attempt toidentify the macroblocks that are prominent to the visual quality of thevideo for a human viewer and attempt to code those macroblocks withhigher quality. The effect of the macroblock level psychovisualenhancements it to take bits away from the less important parts of aframe and apply them to more important parts of the frame. In severalembodiments, enhancements are achieved using three technologies, whichare based on smoothness, brightness and the macroblock SAD. In otherembodiments any of the techniques alone or in combination with anotherof the techniques or another technique entirely can be used.

In one embodiment, all three of the macroblock level psychovisualenhancements described above share a common parameter, S_(MB), whichcontrols the strength of the macroblock level psychovisual enhancement.The maximum and minimum quantizer for the macroblocks are then derivedfrom the strength parameter and the frame quantizer Q_(frame) via thecalculations shown below:

${Q_{{MB}\;{Max}} = \frac{Q_{frame}}{\left( {1 - S_{MB}} \right)}},{and}$Q_(MB Min) = Q_(frame) ⋅ (1 − S_(MB))

where

Q_(MBMax) is the maximum quantizer

Q_(MBMax) is the minimum quantizer

The values Q_(MBMax) and Q_(MBMax) define the upper and lower bounds tothe macroblock quantizers for the entire frame. In one embodiment, theoption of setting the value S_(MB) to any of the values 0.2, 0.3 and 0.4is provided. In other embodiments, other values for S_(MB) can beutilized.

-   -   3.5.4.3.1. Brightness Enhancement

In embodiments where psychovisual enhancement is performed based on thebrightness of the macroblocks, the encoder attempts to encode brightermacroblocks with greater quality. The theoretical basis of thisenhancement is that relatively dark parts of the frame are more or lessignored by human viewers. This macroblock psychovisual enhancement isapplied to I frames and P frames of the video track. For each frame, theencoder looks through the whole frame first. The average brightness (BR) is calculated and the average difference of brightness from theaverage ( DBR) is also calculated. These values are then used to developtwo thresholds (T_(BRLower), T_(BRUpper)), which can be used asindicators for whether the psychovisual enhancement should be applied:T _(BRLower) = BR− DBRT _(BRUpper) = BR +( BR−T _(BRLower))

The brightness enhancement is then applied based on the two thresholdsusing the conditions stated below to generate an intended quantizer(Q_(MB)) for the macroblock:Q _(MB) =Q _(MBMin) when BR>T _(BRUpper)Q _(MB) =Q _(frame) when T _(BRLower) ≦BR≦T _(BRUpper), andQ _(MB) =Q _(MBMax) when BR<T _(BRLower)

where

BR is the brightness value for that particular macroblock

In embodiments where the encoder is compliant with the MPEG-4 standard,the macroblock level psychovisual brightness enhancement techniquecannot change the quantizer by more than ±2 from one macroblock to thenext one. Therefore, the calculated Q_(MB) may require modificationbased upon the quantizer used in the previous macroblock.

-   -   3.5.4.3.2. Smoothness Enhancement

Encoders in accordance with embodiments of the present invention thatinclude a smoothness psychovisual enhancement, modify the quantizerbased on the spatial variation of the image being encoded. Use of asmoothness psychovisual enhancement can be motivated by the theory thathuman vision has an increased sensitivity to quantization artifacts insmooth parts of an image. Smoothness psychovisual enhancement can,therefore, involve increasing the number of bits to represent smootherportions of the image and decreasing the number of bits where there is ahigh degree of spatial variation in the image.

In one embodiment, the smoothness of a portion of an image is measuredas the average difference in the luminance of pixels in a macroblock tothe brightness of the macroblock ( DR). A method of performingsmoothness psychovisual enhancement on an I frame in accordance withembodiments of the present invention is shown in FIG. 3.6. The process540, involves examining the entire frame to calculate (542) DR. Thethreshold for applying the smoothness enhancement, T_(DR), can then bederived (544) using the following calculation:

$T_{DR} = \frac{\overset{\_}{DR}}{2}$

The following smoothness enhancement is performed (546) based on thethreshold.Q _(MB) =Q _(frame) when DR≧T _(DR), andQ _(MB) =Q _(MBMin) when DR<T _(DR)

where

Q_(MB) is the intended quantizer for the macroblock

DR is the deviation value for the macroblock (i.e. mean luminance-meanbrightness)

Embodiments that encode files in accordance with the MPEG-4 standard arelimited as described above in that the macroblock level quantizer changecan be at most ±2 from one macroblock to the next.

-   -   3.5.4.3.3. Macroblock SAD Enhancement

Encoders in accordance with embodiments of the present invention canutilize a macroblock SAD psychovisual enhancement. A macroblock SADpsychovisual enhancement can be used to increase the detail for staticmacroblocks and allow decreased detail in portions of a frame that areused in a high action scene.

A process for performing a macroblock SAD psychovisual enhancement inaccordance with an embodiment of the present invention is illustrated inFIG. 3.7. The process 570 includes inspecting (572) an entire I frame todetermine the average SAD (i.e. MBSAD) for all of the macroblocks in theentire frame and the average difference of a macroblock's SAD from theaverage (i.e. DMBSAD) is also obtained. In one embodiment, both of thesemacroblocks are averaged over the inter-frame coded macroblocks (i.e.the macroblocks encoded using motion compensation or other dependencieson previous encoded video frames). Two thresholds for applying themacroblock SAD enhancement are then derived (574) from these averagesusing the following formulae:T _(MBSADLower) = MBSAD− DMBSAD, andT _(MBSADUpper) = MBSAD+ DMBSAD

where

T_(MBSADLower) is the lower threshold

T_(MBSADUpper) is the upper threshold, which may be bounded by 1024 ifnecessary

The macroblock SAD enhancement is then applied (576) based on these twothresholds according to the following conditions:Q _(MB) =Q _(MBMax) when MBSAD>T _(MBSADUpper),Q _(MB) =Q _(frame) when T _(MADLower) ≦MBSAD≦T _(MBSADUpper)Q _(MB) =Q _(MBMin) when MBSAD<T _(MBSADLower)

where

Q_(MB) is the intended quantizer for the macroblock

MBSAD is the SAD value for that particular macroblock

Embodiments that encode files in accordance with the MPEG-4specification are limited as described above in that the macroblocklevel quantizer change can be at most ±2 from one macroblock to thenext.

3.5.5. Rate Control

The rate control technique used by an encoder in accordance with anembodiment of the present invention can determine how the encoder usesthe allocated bit rate to encode a video sequence. An encoder willtypically seek to encode to a predetermined bit rate and the ratecontrol technique is responsible for matching the bit rate generated bythe encoder as closely as possible to the predetermined bit rate. Therate control technique can also seek to allocate the bit rate in amanner that will ensure the highest visual quality of the video sequencewhen it is decoded. Much of rate control is performed by adjusting thequantizer. The quantizer determines how finely the encoder codes thevideo sequence. A smaller quantizer will result in higher quality andhigher bit consumption. Therefore, the rate control algorithm seeks tomodify the quantizer in a manner that balances the competing interestsof video quality and bit consumption.

Encoders in accordance with embodiments of the present invention canutilize any of a variety of different rate control techniques. In oneembodiment, a single pass rate control technique is used. In otherembodiments a dual (or multiple) pass rate control technique is used. Inaddition, a ‘video buffer verified’ rate control can be performed asrequired. Specific examples of these techniques are discussed below.However, any rate control technique can be used in an encoder inaccordance with the practice of the present inventions.

-   -   3.5.5.1. One Pass Rate Control

An embodiment of a one pass rate control technique in accordance with anembodiment of the present invention seeks to allow high bit rate peaksfor high motion scenes. In several embodiments, the one pass ratecontrol technique seeks to increase the bit rate slowly in response toan increase in the amount of motion in a scene and to rapidly decreasethe bit rate in response to a reduction in the motion in a scene.

In one embodiment, the one pass rate control algorithm uses twoaveraging periods to track the bit rate. A long-term average to ensureoverall bit rate convergence and a short-term average to enable responseto variations in the amount of action in a scene.

A one pass rate control technique in accordance with an embodiment ofthe present invention is illustrated in FIG. 3.8. The one pass ratecontrol technique 580 commences (582) by initializing (584) the encoderwith a desired bit rate, the video frame rate and a variety of otherparameters (discussed further below). A floating point variable isstored, which is indicative of the quantizer. If a frame requiresquantization (586), then the floating point variable is retrieved (588)and the quantizer obtained by rounding the floating point variable tothe nearest integer. The frame is then encoded (590). Observations aremade during the encoding of the frame that enable the determination(592) of a new quantizer value. The process decides (594) to repeatunless there are no more frames. At which point, the encoding incomplete (596).

As discussed above, the encoder is initialized (584) with a variety ofparameters. These parameters are the ‘bit rate’, the ‘frame rate’, the‘Max Key Frame Interval’, the ‘Maximum Quantizer’, the ‘MinimumQuantizer’, the ‘averaging period’, the ‘reaction period’ and the‘down/up ratio’. The following is a discussion of each of theseparameters.

-   -   3.5.5.1.1. The ‘Bit Rate’

The ‘bit rate’ parameter sets the target bit rate of the encoding.

-   -   3.5.5.1.2. The ‘Frame Rate’

The ‘frame rate’ defines the period between frames of video.

-   -   3.5.5.1.3. The ‘Max Key Frame Interval’

The ‘Max Key Frame Interval’ specifies the maximum interval between thekey frames. The key frames are normally automatically inserted in theencoded video when the codec detects a scene change. In circumstanceswhere a scene continues for a long interval without a single cut, keyframes can be inserted in insure that the interval between key frames isalways less or equal to the ‘Max Key Frame Interval’. In one embodiment,the ‘Max Key Frame Interval’ parameter can be set to a value of 300frames. In other embodiments, other values can be used.

-   -   3.5.5.1.4. The ‘Maximum Quantizer’ and the ‘Minimum Quantizer’

The ‘Maximum Quantizer’ and the ‘Minimum Quantizer’ parameters set theupper and lower bound of the quantizer used in the encoding. In oneembodiment, the quantizer bounds are set at values between 1 and 31.

-   -   3.5.5.1.5. The ‘Averaging Period’

The ‘averaging period’ parameter controls the amount of video that isconsidered when modifying the quantizer. A longer averaging period willtypically result in the encoded video having a more accurate overallrate. In one embodiment, an ‘averaging period’ of 2000 is used. Althoughin other embodiments other values can be used.

-   -   3.5.5.1.6. The ‘Reaction Period’

The ‘reaction period’ parameter determines how fast the encoder adaptsto changes in the motion in recent scenes. A longer ‘reaction period’value can result in better quality high motion scenes and worse qualitylow motion scenes. In one embodiment, a ‘reaction period’ of 10 is used.Although in other embodiments other values can be used.

-   -   3.5.5.1.7. The ‘Down/Up Ratio’

The ‘down/up ratio’ parameter controls the relative sensitivity for thequantizer adjustment in reaction to the high or low motion scenes. Alarger value typically results in higher quality high motion scenes andincreased bit consumption. In one embodiment, a ‘down/up ratio’ of 20 isused. Although in other embodiments, other values can be used.

-   -   3.5.5.1.8. Calculating the Quantizer Value

As discussed above, the one pass rate control technique involves thecalculation of a quantizer value after the encoding of each frame. Thefollowing is a description of a technique in accordance with anembodiment of the present invention that can be used to update thequantizer value.

The encoder maintains two exponential moving averages having periodsequal to the ‘averaging period’ (P_(average)) and the ‘reaction period’(P_(reaction)) a moving average of the bit rate. The two exponentialmoving averages can be calculated according to the relationship:

$A_{t} = {{A_{t - 1} \cdot \frac{P - T}{P}} + {B \cdot \frac{T}{P}}}$

where

A_(t) is the average at instance t;

A_(t−1) is the average at instance t−T (usually the average in theprevious frame);

T represents the interval period (usually the frame time); and

P is the average period, which can be either P_(average) and orP_(reaction).

The above calculated moving average is then adjusted into bit rate bydividing by the time interval between the current instance and the lastinstance in the video, using the following calculation:

$R_{t} = {A_{t}\frac{1}{T}}$

where

R_(t) is the bitrate;

A_(t) is either of the moving averages; and

T is the time interval between the current instance and last instance(it is usually the inverse of the frame rate).

The encoder can calculate the target bit rate (R_(target)) of the nextframe as follows:R _(target) =R _(overall)+(R _(overall) −R _(average))

where

R_(overall) is the overall bit rate set for the whole video; and

R_(average) is the average bit rate using the long averaging period.

In several embodiments, the target bit rate is lower bounded by 75% ofthe overall bit rate. If the target bit rate drops below that bound,then it will be forced up to the bound to ensure the quality of thevideo.

The encoder then updates the internal quantizer based on the differencebetween R_(target) and R_(reaction). If R_(reaction) is less thanR_(target), then there is a likelihood that the previous frame was ofrelatively low complexity. Therefore, the quantizer can be decreased byperforming the following calculation:

$Q_{internal}^{\prime} = {Q_{internal} \cdot \left( {1 - \frac{1}{P_{reation}}} \right)}$

When R_(reaction) is greater than R_(target), there is a significantlikelihood that previous frame possessed a relatively high level ofcomplexity. Therefore, the quantizer can be increased by performing thefollowing calculation:

$Q_{internal}^{\prime} = {Q_{internal} \cdot \left( {1 + \frac{1}{{SP}_{reaction}}} \right)}$

where

S is the ‘up/down ratio’.

-   -   3.5.5.1.9. B-VOP Encoding

The algorithm described above can also be applied to B-VOP encoding.When B-VOP is enabled in the encoding, the quantizer for the B-VOP(Q_(B)) is chosen based on the quantizer of the P-VOP (Q_(P)) followingthe B-VOP. The value can be obtained in accordance with the followingrelationships:

$\begin{matrix}{Q_{B} = {{{2 \cdot Q_{P}}\mspace{14mu}{for}\mspace{14mu} Q_{P}} \leq 4}} \\{Q_{B} = {{5 + {{\frac{3}{4} \cdot Q_{P}}\mspace{14mu}{for}\mspace{14mu} 4}} < Q_{P} \leq 20}} \\{Q_{B} = {{Q_{P}\mspace{14mu}{for}\mspace{14mu} Q_{P}} \geq 20}}\end{matrix}$

-   -   3.5.5.2. Two Pass Rate Control

Encoders in accordance with an embodiment of the present invention thatuse a two (or multiple) pass rate control technique can determine theproperties of a video sequence in a first pass and then encode the videosequence with knowledge of the properties of the entire sequence.Therefore, the encoder can adjust the quantization level for each framebased upon its relative complexity compared to other frames in the videosequence.

A two pass rate control technique in accordance with an embodiment ofthe present invention, the encoder performs a first pass in which thevideo is encoded in accordance with the one pass rate control techniquedescribed above and the complexity of each frame is recorded (any of avariety of different metrics for measuring complexity can be used). Theaverage complexity and, therefore, the average quantizer (Q_(ref)) canbe determined based on the first. In the second pass, the bit stream isencoded with quantizers determined based on the complexity valuescalculated during the first pass.

-   -   3.5.5.2.1. Quantizers for I-VOPs

The quantizer Q for I-VOPs is set to 0.75×Q_(ref), provided the nextframe is not an I-VOP. If the next frame is also an I-VOP, the Q (forthe current frame) is set to 1.25×Q_(ref).

-   -   3.5.5.2.2. Quantizers for P-VOPs

The quantizer for the P-VOPs can be determined using the followingexpression.

$Q = {F^{- 1}\left\{ {{F\left( Q_{ref} \right)} \cdot \left( {\overset{\_}{C_{complexity}}/C_{complexity}} \right)^{k}} \right\}}$

where

C_(complexity) is the complexity of the frame;

C_(complexity) is the average complexity of the video sequence;

F(x) is a function that provides the number which the complexity of theframe must be multiplied to give the number of bits required to encodethe frame using a quantizer with a quantization value x;

F⁻¹(x) is the inverse function of F(x); and

k is the strength parameter.

The following table defines an embodiment of a function F(Q) that can beused to generator the factor that the complexity of a frame must bemultiplied by in order to determine the number of bits required toencode the frame using an encoder with a quantizer Q.

TABLE 6 Values of F(Q) with respect to Q. Q F(Q) 1 1 2 0.4 3 0.15 4 0.085 0.05 6 0.032 7 0.022 8 0.017 9 0.013 10 0.01 11 0.008 12 0.0065 130.005 14 0.0038 15 0.0028 16 0.002

If the strength parameter k is chosen to be 0, then the result is aconstant quantizer. When the strength parameter is chosen to be 1, thequantizer is proportional to C_(complexity). Several encoders inaccordance with embodiments of the present invention have a strengthparameter k equal to 0.5.

-   -   3.5.5.2.3. Quantizers for B-VOPs

The quantizer Q for the B-VOPs can be chosen using the same techniquefor choosing the quantizer for B-VOPs in the one pass techniquedescribed above.

-   -   3.5.5.3. Video Buffer Verified Rate Control

The number of bits required to represent a frame can vary depending onthe characteristics of the video sequence. Most communication systemsoperate at a constant bit rate. A problem that can be encountered withvariable bit rate communications is allocating sufficient resources tohandle peaks in resource usage. Several encoders in accordance withembodiments of the present invention encode video with a view topreventing overflow of a decoder video buffer, when the bit rate of thevariable bit rate communication spikes.

The objectives of video buffer verifier (VBV) rate control can includegenerating video that will not exceed a decoder's buffer whentransmitted. In addition, it can be desirable that the encoded videomatch a target bit rate and that the rate control produces high qualityvideo.

Encoders in accordance with several embodiments of the present inventionprovide a choice of at least two VBV rate control techniques. One of theVBV rate control techniques is referred to as causal rate control andthe other technique is referred to as Nth pass rate control.

-   -   3.5.5.3.1. Causal Rate Control

Causal VBV rate control can be used in conjunction with a one pass ratecontrol technique and generates outputs simply based on the current andprevious quantizer values.

An encoder in accordance with an embodiment of the present inventionincludes causal rate control involving setting the quantizer for frame n(i.e. Q_(n)) according to the following relationship.

$\frac{1}{Q_{n}^{\prime}} = {\frac{1}{Q_{n - 1}^{\prime}} + X_{bitrate} + X_{velocity} + X_{size}}$$\frac{1}{Q_{n}} = {\frac{1}{Q_{n}^{\prime}} + X_{drift}}$

where

Q′_(n) is the quantizer estimated by the single pass rate control;

X_(bitrate) is calculated by determining a target bit rate based on thedrift from the desired bit rate;

X_(velocity) is calculated based on the estimated time until the VBVbuffer over- or under-flows;

X_(size) is applied on the result of P-VOPs only and is calculated basedon the rate at which the size of compressed P-VOPs is changing overtime;

X_(drift) is the drift from the desired bit rate.

In several embodiments, the causal VBV rate control may be forced todrop frames and insert stuffing to respect the VBV model. If acompressed frame unexpectedly contains too many or two few bits, then itcan be dropped or stuffed.

-   -   3.5.5.3.2. Nth Pass VBV Rate Control

Nth pass VBV rate control can be used in conjunction with a multiplepass rate control technique and it uses information garnered duringprevious analysis of the video sequence. Encoders in accordance withseveral embodiments of the present invention perform Nth pass VBV ratecontrol according to the process illustrated in FIG. 3.9. The process600 commences with the first pass, during which analysis (602) isperformed. Map generation is performed (604) and a strategy is generated(606). The nth pass Rate Control is then performed (608).

-   -   3.5.5.3.3. Analysis

In one embodiment, the first pass uses some form of causal rate controland data is recorded for each frame concerning such things as theduration of the frame, the coding type of the frame, the quantizer used,the motion bits produced and the texture bits produced. In addition,global information such as the timescale, resolution and codec settingscan also be recorded.

-   -   3.5.5.3.4. Map Generation

Information from the analysis is used to generate a map of the videosequence. The map can specify the coding type used for each frame(I/B/P) and can include data for each frame concerning the duration ofthe frame, the motion complexity and the texture complexity. In otherembodiments, the map may also contain information enabling betterprediction of the influence of quantizer and other parameters oncompressed frame size and perceptual distortion. In several embodiments,map generation is performed after the N−1th pass is completed.

-   -   3.5.5.3.5. Strategy Generation

The map can be used to plan a strategy as to how the Nth pass ratecontrol will operate. The ideal level of the VBV buffer after everyframe is encoded can be planned. In one embodiment, the strategygeneration results in information for each frame including the desiredcompressed frame size, an estimated frame quantizer. In severalembodiments, strategy generation is performed after map generation andprior to the Nth pass.

In one embodiment, the strategy generation process involves use of aniterative process to simulate the encoder and determine desiredquantizer values for each frame by trying to keep the quantizer as closeas possible to the median quantizer value. A binary search can be usedto generate a base quantizer for the whole video sequence. The basequantizer is the constant value that causes the simulator to achieve thedesired target bit rate. Once the base quantizer is found, the strategygeneration process involves consideration of the VBV constrains. In oneembodiment, a constant quantizer is used if this will not modify the VBVconstrains. In other embodiments, the quantizer is modulated based onthe complexity of motion in the video frames. This can be furtherextended to incorporate masking from scene changes and other temporaleffects.

3.5.5.3.6. In-loop Nth Pass Rate Control

In one embodiment, the in-loop Nth pass rate control uses the strategyand uses the map to make the best possible prediction of the influenceof quantizer and other parameters on compressed frame size andperceptual distortion. There can be a limited discretion to deviate fromthe strategy to take short-term corrective strategy. Typically,following the strategy will prevent violation of the VBV model. In oneembodiment, the in-loop Nth pass rate control uses a PID control loop.The feedback in the control loop is the accumulated drift from the idealbitrate.

Although the strategy generation does not involve dropping frames, thein-loop Nth rate control may drop frames if the VBV buffer wouldotherwise underflow. Likewise, the in-loop Nth pass rate control canrequest video stuffing to be inserted to prevent VBV overflow.

3.5.6. Predictions

In one embodiment, AD/DC prediction is performed in a manner that iscompliant with the standard referred to as ISO/IEC 14496-2:2001(E),section 7.4.3. (DC and AC prediction) and 7.7.1. (field DC and ACprediction).

3.5.7. Texture Coding

An encoder in accordance with an embodiment of the present invention canperform texture coding in a manner that is compliant with the standardreferred to as ISO/IEC 14496-2:2001(E), annex B (variable length codes)and 7.4.1. (variable length decoding).

3.5.8. Motion Coding

An encoder in accordance with an embodiment of the present invention canperform motion coding in a manner that is compliant with the standardreferred to as ISO/IEC 14496-2:2001(E), annex B (variable length codes)and 7.6.3. (motion vector decoding).

3.5.9. Generating ‘Video’ Chunks

The video track can be considered a sequence of frames 1 to N. Systemsin accordance with embodiments of the present invention are capable ofencoding the sequence to generate a compressed bitstream. The bitstreamis formatted by segmenting it into chunks 1 to N. Each video frame n hasa corresponding chunk n.

The chunks are generated by appending bits from the bitstream to chunk nuntil it, together with the chunks 1 through n−1 contain sufficientinformation for a decoder in accordance with an embodiment of thepresent invention to decode the video frame n. In instances wheresufficient information is contained in chunks 1 through n−1 to generatevideo frame n, an encoder in accordance with embodiments of the presentinvention can include a marker chunk. In one embodiment, the markerchunk is a not-coded P-frame with identical timing information as theprevious frame.

3.6. Generating ‘Subtitle’ Chunks

An encoder in accordance with an embodiment of the present invention cantake subtitles in one of a series of standard formats and then convertsthe subtitles to bit maps. The information in the bit maps is thencompressed using run length encoding. The run length encoded bit mapsare the formatted into a chunk, which also includes informationconcerning the start time and the stop time for the particular subtitlecontained within the chunk. In several embodiments, informationconcerning the color, size and position of the subtitle on the screencan also be included in the chunk. Chunks can be included into thesubtitle track that set the palette for the subtitles and that indicatethat the palette has changed. Any application capable of generating asubtitle in a standard subtitle format can be used to generate the textof the subtitles. Alternatively, software can be used to convert textentered by a user directly into subtitle information.

3.7. Interleaving

Once the interleaver has received all of the chunks described above, theinterleaver builds a multimedia file. Building the multimedia file caninvolve creating a ‘CSET’ chunk, an ‘INFO’ list chunk, a ‘hdrl’ chunk, a‘movi’ list chunk and an idx1 chunk. Methods in accordance withembodiments of the present invention for creating these chunks and forgenerating multimedia files are described below.

3.7.1. Generating a ‘CSET’ Chunk

As described above, the ‘CSET’ chunk is optional and can generated bythe interleaver in accordance with the AVI Container FormatSpecification.

3.7.2. Generating a ‘INFO’ List Chunk

As described above, the ‘INFO’ list chunk is optional and can begenerated by the interleaver in accordance with the AVI Container FormatSpecification.

3.7.3. Generating the ‘hdrl’ List Chunk

The ‘hdrl’ list chunk is generated by the interleaver based on theinformation in the various chunks provided to the interleaver. The‘hdrl’ list chunk references the location within the file of thereferenced chunks. In one embodiment, the ‘hdrl’ list chunk uses fileoffsets in order to establish references.

3.7.4. Generating the ‘Movi’ List Chunk

As described above, ‘movi’ list chunk is created by encoding audio,video and subtitle tracks to create ‘audio’, ‘video’ and ‘subtitle’chunks and then interleaving these chunks. In several embodiments, the‘movi’ list chunk can also include digital rights managementinformation.

-   -   3.7.4.1. Interleaving the Video/Audio/Subtitles

A variety of rules can be used to interleave the audio, video andsubtitle chunks. Typically, the interleaver establishes a number ofqueues for each of the video and audio tracks. The interleaverdetermines which queue should be written to the output file. The queueselection can be based on the interleave period by writing from thequeue that has the lowest number of interleave periods written. Theinterleaver may have to wait for an entire interleave period to bepresent in the queue before the chunk can be written to the file.

In one embodiment, the generated ‘audio,’ ‘video’ and ‘subtitle’ chunksare interleaved so that the ‘audio’ and ‘subtitle’ chunks are locatedwithin the file prior to the ‘video’ chunks containing informationconcerning the video frames to which they correspond. In otherembodiments, the ‘audio’ and ‘subtitle’ chunks can be located after the‘video’ chunks to which they correspond. The time differences betweenthe location of the ‘audio,’ ‘video’ and ‘subtitle’ chunks is largelydependent upon the buffering capabilities of players that are used toplay the devices. In embodiments where buffering is limited or unknown,the interleaver interleaves the ‘audio,’ ‘video’ and ‘subtitle’ chunkssuch that the ‘audio’ and ‘subtitle’ chunks are located between ‘video’chunks, where the ‘video’ chunk immediately following the ‘audio’ and‘subtitle’ chunk contains the first video frame corresponding to theaudio or subtitle.

-   -   3.7.4.2. Generating DRM Information

In embodiments where DRM is used to protect the video content of amultimedia file, the DRM information can be generated concurrently withthe encoding of the video chunks. As each chunk is generated, the chunkcan be encrypted and a DRM chunk generated containing informationconcerning the encryption of the video chunk.

-   -   3.7.4.3. Interleaving the DRM Information

An interleaver in accordance with an embodiment of the present inventioninterleaves a DRM chunk containing information concerning the encryptionof a video chunk prior to the video chunk. In one embodiment, the DRMchunk for video chunk n is located between video chunk n−1 and videochunk n. In other embodiments, the spacing of the DRM before and afterthe video chunk n is dependent upon the amount of buffering providedwithin device decoding the multimedia file.

3.7.5. Generating the ‘idx1’ Chunk

Once the ‘movi’ list chunk has been generated, the generation of the‘idx1’ chunk is a simple process. The ‘idx1’ chunk is created by readingthe location within the ‘movi’ list chunk of each ‘data’ chunk. Thisinformation is combined with information read from the ‘data’ chunkconcerning the track to which the ‘data’ chunk belongs and the contentof the ‘data’ chunk. All of this information is then inserted into the‘idx1’ chunk in a manner appropriate to whichever of the formatsdescribed above is being used to represent the information.

4. Transmission and Distribution of Multimedia File

Once a multimedia file is generated, the file can be distributed overany of a variety of networks. The fact that in many embodiments theelements required to generate a multimedia presentation and menus,amongst other things, are contained within a single file simplifiestransfer of the information. In several embodiments, the multimedia filecan be distributed separately from the information required to decryptthe contents of the multimedia file.

In one embodiment, multimedia content is provided to a first server andencoded to create a multimedia file in accordance with the presentinvention. The multimedia file can then be located either at the firstserver or at a second server. In other embodiments, DRM information canbe located at the first server, the second server or a third server. Inone embodiment, the first server can be queried to ascertain thelocation of the encoded multimedia file and/or to ascertain the locationof the DRM information.

5. Decoding Multimedia File

Information from a multimedia file in accordance with an embodiment ofthe present invention can be accessed by a computer configured usingappropriate software, a dedicated player that is hardwired to accessinformation from the multimedia file or any other device capable ofparsing an AVI file. In several embodiments, devices can access all ofthe information in the multimedia file. In other embodiments, a devicemay be incapable of accessing all of the information in a multimediafile in accordance with an embodiment of the present invention. In aparticular embodiment, a device is not capable of accessing any of theinformation described above that is stored in chunks that are notspecified in the AVI file format. In embodiments where not all of theinformation can be accessed, the device will typically discard thosechunks that are not recognized by the device.

Typically, a device that is capable of accessing the informationcontained in a multimedia file in accordance with an embodiment of thepresent invention is capable of performing a number of functions. Thedevice can display a multimedia presentation involving display of videoon a visual display, generate audio from one of potentially a number ofaudio tracks on an audio system and display subtitles from potentiallyone of a number of subtitle tracks. Several embodiments can also displaymenus on a visual display while playing accompanying audio and/or video.These display menus are interactive, with features such as selectablebuttons, pull down menus and sub-menus. In some embodiments, menu itemscan point to audio/video content outside the multimedia file presentlybeing accessed. The outside content may be either located local to thedevice accessing the multimedia file or it may be located remotely, suchas over a local area, wide are or public network. Many embodiments canalso search one or more multimedia files according to ‘meta data’included within the multimedia file(s) or ‘meta data’ referenced by oneor more of the multimedia files.

5.1. Display of Multimedia Presentation

Given the ability of multimedia files in accordance with embodiments ofthe present invention to support multiple audio tracks, multiple videotracks and multiple subtitle tracks, the display of a multimediapresentation using such a multimedia file that combines video, audioand/or subtitles can require selection of a particular audio track,video track and/or subtitle track either through a visual menu system ora pull down menu system (the operation of which are discussed below) orvia the default settings of the device used to generate the multimediapresentation. Once an audio track, video track and potentially asubtitle track are selected, the display of the multimedia presentationcan proceed.

A process for locating the required multimedia information from amultimedia file including DRM and displaying the multimedia informationin accordance with an embodiment of the present invention is illustratedin FIG. 4.0. The process 620 includes obtaining the encryption keyrequired to decrypt the DRM header (622). The encryption key is thenused to decrypt (624) the DRM header and the first DRM chunk is located(626) within the ‘movi’ list chunk of the multimedia file. Theencryption key required to decrypt the ‘DRM’ chunk is obtained (628)from the table in the ‘DRM’ header and the encryption key is used todecrypt an encrypted video chunk. The required audio chunk and anyrequired subtitle chunk accompany the video chunk are then decoded (630)and the audio, video and any subtitle information are presented (632)via the display and the sound system.

In several embodiments the chosen audio track can include multiplechannels to provide stereo or surround sound audio. When a subtitletrack is chosen to be displayed, a determination can be made as towhether the previous video frame included a subtitle (this determinationmay be made in any of a variety of ways that achieves the outcome ofidentifying a previous ‘subtitle’ chunk that contained subtitleinformation that should be displayed over the currently decoded videoframe). If the previous subtitle included a subtitle and the timinginformation for the subtitle indicates that the subtitle should bedisplayed with the current frame, then the subtitle is superimposed onthe decoded video frame. If the previous frame did not include asubtitle or the timing information for the subtitle on the previousframe indicates that the subtitle should not be displayed in conjunctionwith the currently decoded frame, then a ‘subtitle’ chunk for theselected subtitle track is sought. If a ‘subtitle’ chunk is located,then the subtitle is superimposed on the decoded video. The video(including any superimposed subtitles) is then displayed with theaccompanying audio.

Returning to the discussion of FIG. 4.0., the process determines (634)whether there are any additional DRM chunks. If there are, then the nextDRM chunk is located (626) and the process continues until no additionalDRM chunks remain. At which point, the presentation of the audio, videoand/or subtitle tracks is complete (636).

In several embodiments, a device can seek to a particular portion of themultimedia information (e.g. a particular scene of a movie with aparticular accompanying audio track and optionally a particularaccompanying subtitle track) using information contained within the‘hdrl’ chunk of a multimedia file in accordance with the presentinvention. In many embodiments, the decoding of the ‘video’ chunk,‘audio’ chunk and/or ‘subtitle’ chunk can be performed in parallel withother tasks.

An example of a device capable of accessing information from themultimedia file and displaying video in conjunction with a particularaudio track and/or a particular subtitle track is a computer configuredin the manner described above using software. Another example is a DVDplayer equipped with a codec that includes these capabilities. In otherembodiments, any device configured to locate or select (whetherintentionally or arbitrarily) ‘data’ chunks corresponding to particularmedia tracks and decode those tracks for presentation is capable ofgenerating a multimedia presentation using a multimedia file inaccordance with the practice of the present invention.

In several embodiments, a device can play multimedia information from amultimedia file in combination with multimedia information from anexternal file. Typically, such a device would do so by sourcing an audiotrack or subtitle track from a local file referenced in a multimediafile of the type described above. If the referenced file is not storedlocally and the device is networked to the location where the device isstored, then the device can obtain a local copy of the file. The devicewould then access both files, establishing a video, an audio and asubtitle (if required) pipeline into which the various tracks ofmultimedia are fed from the different file sources.

5.1.1. Non-sequential Display of Multimedia Presentation

Many embodiments of decoders in accordance with the present inventionare capable of displaying a multimedia presentation contained within amultimedia file non-sequentially. Non-sequential display can includeplaying the sequence in reverse and/or increasing the apparent speedwith which the sequence is displayed by skipping frames in the sequence.Non-sequential display can also include skipping in an irregular fashionbetween different portions of a multimedia presentation.

In several embodiments, the decoder uses an ‘index’ chunk within the‘DXDT’ of a multimedia file to locate particular encoded video frames.Knowledge of the location of specific encoded video frames can be usedto skip frames either in a regular fashion (such as during fastforwarding or rewinding) or in an irregular fashion (such as whenskipping between scenes or chapters).

A process that can be used in accordance with an embodiment of themethod of the invention to locate a specific video frame using an‘index’ chunk is shown in FIG. 4.0.1. The process 640 commences with theidentification (641 a) of the particular frame in a video sequence thatis being sought. A search (641 b) can then be performed through an‘index’ chunk to locate the ‘tag’ chunk that references a video frameclosest to the frame being sought. In one embodiment, the closestpreceding video frame is sought. Once the closest video frame has beenlocated, information within the ‘tag’ chunk can be used to provide (641c) information concerning the location of the encoded video framereferenced by the ‘tag’ chunk within the multimedia file. In manyembodiments, information within the ‘tag’ chunk can also be used tolocate information concerning the encoded video frame within the ‘idx1’chunk. Knowing the corresponding location of the ‘idx1’ chunk canincrease search time through the ‘idx1’ chunk, when attempting to locateassociated information.

A process for locating the ‘tag’ chunk within an ‘index’ chunk thatreferences the preceding frame closest to a desired video frame within avideo sequence is shown in FIG. 4.0.2. The process 142 commences withthe identification (143 a) of a current ‘tag’ chunk. The current ‘tag’chunk is typically the first chunk in the ‘index’ chunk. The position ofthe desired video frame relative to the video frame referenced by thecurrent ‘tag’ chunk is then determined (143 b). The process thenattempts (143 c) to locate a next ‘tag’ chunk. If there are no more‘tag’ chunks remaining in the ‘index’ chunk, then the search is complete(143 d). In one embodiment, the position of the encoded video frameand/or audio information referenced by the last ‘tag’ chunk in the‘index’ chunk is returned. In other embodiments, such as embodimentswhere the last frame of the video sequence is referenced by a ‘tag’chunk, the inability to locate a next ‘tag’ chunk is an indication thateither the encoded video frame could not be located in the multimediafile or that an error has occurred.

When a next ‘tag’ chunk can be located from within the ‘index’ chunk,the process compares (143 e) the positions of the encoded video framereferenced by the next ‘tag’ chunk and the desired video chunk. Adecision (143 f) is then made based upon whether the desired video framelies between the encoded video frames in the sequence referenced by thecurrent and next ‘tag’ chunks. If the desired video frame lies betweenthe referenced frames, then the position of the video frame and anyaudio referenced by the current ‘tag’ chunk within the multimedia fileare returned (143 g) by the process.

When the desired video frame is not located between the framesreferenced by the current and next ‘tag’ chunks, then the next ‘tag’chunk becomes (143 h) the current ‘tag’ chunk. The process repeats (143a) until the condition that the desired video frame be located betweenthe encoded video frames referenced by the current and next ‘tag’ chunksis satisfied (143 g) or all of the ‘tag’ chunks have been inspected (143d).

In further embodiments, the location of a desired frame can be furtherrefined by using the references within the ‘index’ chunk to thecorresponding information within the ‘idx1’ chunk to search for areference within the ‘idx1’ chunk to a specifically desired encodedvideo frame that is not referenced in the ‘index’ chunk.

Although the processes shown in FIGS. 4.0.1. and 4.0.2. are discussedwith reference to the location of a desired video frame, similarprocesses in accordance with an embodiment of the invention could alsobe used to locate a desired portion of one or more audio or subtitletracks. In addition, similar processes in accordance with embodiments ofthe present invention can be used to locate the video frame, portion ofaudio track or portion of subtitle track referenced in an ‘index’ chunkthat is closest to a particular time, where the time is measuredrelative to the running time of a video, audio or multimediapresentation stored within a multimedia file. Furthermore, similarprocesses can be used to locate information within the ‘idx1’ chunk.

5.2. Generation of Menus

A decoder in accordance with an embodiment of the present invention isillustrated in FIG. 4.1. The decoder 650 processes a multimedia file 652in accordance with an embodiment of the present invention by providingthe file to a demultiplexer 654. The demultiplexer extracts the ‘DMNU’chunk from the multimedia file and extracts all of the ‘LanguageMenus’chunks from the ‘DMNU’ chunk and provides them to a menu parser 656. Thedemultiplexer also extracts all of the ‘Media’ chunks from the ‘DMNU’chunk and provides them to a media renderer 658. The menu parser 656parses information from the ‘LanguageMenu’ chunks to build a statemachine representing the menu structure defined in the ‘LanguageMenu’chunk. The state machine representing the menu structure can be used toprovide displays to the user and to respond to user commands. The statemachine is provided to a menu state controller 660. The menu statecontroller keeps track of the current state of the menu state machineand receives commands from the user. The commands from the user cancause a state transition. The initial display provided to a user and anyupdates to the display accompanying a menu state transition can becontrolled using a menu player interface 662. The menu player interface662 can be connected to the menu state controller and the media render.The menu player interface instructs the media renderer which mediashould be extracted from the media chunks and provided to the user viathe player 664 connected to the media renderer. The user can provide theplayer with instructions using an input device such as a keyboard, mouseor remote control. Generally the multimedia file dictates the menuinitially displayed to the user and the user's instructions dictate theaudio and video displayed following the generation of the initial menu.The system illustrated in FIG. 4.1. can be implemented using a computerand software. In other embodiments, the system can be implemented usingfunction specific integrated circuits or a combination of software andfirmware.

An example of a menu in accordance with an embodiment of the presentinvention is illustrated in FIG. 4.2. The menu display 670 includes fourbutton areas 672, background video 674, including a title 676, and apointer 678. The menu also includes background audio (not shown). Thevisual effect created by the display can be deceptive. The visualappearance of the buttons is typically part of the background video andthe buttons themselves are simply defined regions of the backgroundvideo that have particular actions associated with them, when the regionis activated by the pointer. The pointer is typically an overlay.

FIG. 4.3. conceptually illustrates the source of all of the informationin the display shown in FIG. 4.2. The background video 674 can include amenu title, the visual appearance of the buttons and the background ofthe display. All of these elements and additional elements can appearstatic or animated. The background video is extracted by usinginformation contained in a ‘MediaTrack’ chunk 700 that indicates thelocation of background video within a video track 702. The backgroundaudio 706 that can accompany the menu can be located using a‘MediaTrack’ chunk 708 that indicates the location of the backgroundaudio within an audio track 710. As described above, the pointer 678 ispart of an overlay 713. The overlay 713 can also include graphics thatappear to highlight the portion of the background video that appears asa button. In one embodiment, the overlay 713 is obtained using a‘MediaTrack’ chunk 712 that indicates the location of the overlay withina overlay track 714. The manner in which the menu interacts with a useris defined by the ‘Action’ chunks (not shown) associated with each ofthe buttons. In the illustrated embodiment, a ‘PlayAction’ chunk 716 isillustrated. The ‘PlayAction’ chunk indirectly references (the otherchunks referenced by the ‘PlayAction’ chunk are not shown) a scenewithin a multimedia presentation contained within the multimedia file(i.e. an audio, video and possibly a subtitle track). The ‘PlayAction’chunk 716 ultimately references the scene using a ‘MediaTrack’ chunk718, which indicates the scene within the feature track. A point in aselected or default audio track and potentially a subtitle track arealso referenced.

As the user enters commands using the input device, the display may beupdated not only in response to the selection of button areas but alsosimply due to the pointer being located within a button area. Asdiscussed above, typically all of the media information used to generatethe menus is located within the multimedia file and more specificallywithin a ‘DMNU’ chunk. Although in other embodiments, the informationcan be located elsewhere within the file and/or in other files.

5.3. Access the Meta Data

‘Meta data’ is a standardized method of representing information. Thestandardized nature of ‘Meta data’ enables the data to be accessed andunderstood by automatic processes. In one embodiment, the ‘meta data’ isextracted and provided to a user for viewing. Several embodiments enablemultimedia files on a server to be inspected to provide informationconcerning a users viewing habits and viewing preferences. Suchinformation could be used by software applications to recommend othermultimedia files that a user may enjoy viewing. In one embodiment, therecommendations can be based on the multimedia files contained onservers of other users. In other embodiments, a user can request amultimedia file and the file can be located by a search engine and/orintelligent agents that inspect the ‘meta data’ of multimedia files in avariety of locations. In addition, the user can chose between variousmultimedia files containing a particular multimedia presentation basedon ‘meta data’ concerning the manner in which each of the differentversions of the presentation were encoded.

In several embodiments, the ‘meta data’ of multimedia files inaccordance with embodiments of the present invention can be accessed forpurposes of cataloging or for creating a simple menu to access thecontent of the file.

While the above description contains many specific embodiments of theinvention, these should not be construed as limitations on the scope ofthe invention, but rather as an example of one embodiment thereof. Forexample, a multimedia file in accordance with an embodiment of thepresent invention can include a single multimedia presentation ormultiple multimedia presentations. In addition, such a file can includeone or more menus and any variety of different types of ‘meta data’.Accordingly, the scope of the invention should be determined not by theembodiments illustrated, but by the appended claims and theirequivalents.

What is claimed is:
 1. A decoder for decoding a multimedia filecomprising at least one video track and at least one audio track, thedecoder comprising: a processor; and memory having a multimedia fileincluding: a series of encoded video frames; a first index that includesinformation indicative of the location within the file andcharacteristics of each encoded video frame; and a separate second indexthat includes information indicative of the location within the file ofa subset of the encoded video frames, the separate second index locatedprior to the series of encoded video frames and the first index, thefirst and second indexes enabling trick play functionality.
 2. Thedecoder of claim 1, wherein: the second index includes at least one tagthat references an encoded video frame in the subset of encoded videoframes; each tag comprises: the location within the file of thereferenced encoded video frame; the frame number of the encoded videoframe in the sequence of encoded video frames.
 3. The decoder of claim2, wherein the multimedia file further comprises: at least one audiotrack; wherein each tag further comprises a reference to a portion of atleast one of the audio tracks; wherein the portion of the track that isreferenced accompanies the encoded video frame referenced by the tag. 4.The decoder of claim 2, wherein: each tag further comprises a referenceto information located within the first index; and the informationreferenced in the first index is indicative of the location within thefile and characteristics of the encoded video frame referenced by thetag.
 5. The decoder of claim 1 wherein the second index includes aplurality of tags, each tag references encoded video frames that areevenly spaced throughout the encoded video frames.
 6. The decoder ofclaim 1 wherein the second index includes a plurality of tags, each tagreferences encoded video frames that are spaced at least ten secondsapart.
 7. The decoder of claim 1 wherein the second index includes aplurality of tags, each tag includes chunk offset information, indexoffset information, video frame identifiers and audio track identifiers.8. The decoder of claim 1 wherein trick play functionality comprises atleast one of fast forward, rewind and scene skipping.
 9. An encoder forencoding a multimedia file comprising at least one video track and atleast one audio track, the encoder comprising: a processor; a memoryincluding a file containing at least one sequence of encoded videoframes and a full index that includes information indicative of thelocation within the file and characteristics of each encoded videoframe; wherein the processor is configured to generate an abridged indexthat references a subset of the encoded video frames in the sequence ofencoded video frames and to encode a multimedia file including theabridged index, the at least one sequence of encoded video frames, and afull index so that the abridged index is located within the multimediafile prior to the series of encoded video frames, the first and secondindexes enabling trick play functionality.
 10. The encoder of claim 9,wherein: the processor is configured to generate a complete index thatreferences all of the encoded video frames in the sequence of encodedvideo frames; and each reference to an encoded video frame in theabridged index includes a reference to the reference to that frame inthe complete index.
 11. The encoder of claim 9, wherein each referenceto an encoded video frame in the abridged index includes the sequencenumber of the encoded video frame.
 12. The encoder of claim 11, whereinthe processor is configured to include in each reference to an encodedvideo frame a reference to a location within at least one sound track.13. The encoder of claim 9 wherein the processor is configured to insertkey frames when one of the processor detects a scene change and athreshold interval of video frames is exceeded without the processordetecting a scene change.
 14. The encoder of claim 9 wherein trick playfunctionality comprises at least one of fast forward, rewind and sceneskipping.
 15. A decoder for decoding multimedia comprising at least onevideo track and at least one audio track, the decoder comprising: aprocessor configured to decode multimedia; wherein the multimediaincludes: a sequence of encoded video frames; a complete indexreferencing each encoded video frame in the sequence of encoded videoframes; an abridged index referencing a subset of the encoded videoframes in the sequence of encoded video frames; wherein the processor isconfigured to locate a particular encoded video frame within themultimedia using the abridged index and to playback the sequence ofencoded video frame starting from the located encoded video frame, thefirst and second indexes enabling trick play functionality.
 16. Thedecoder of claim 15, wherein the processor is configured to locatereference information in the complete index using the abridged index.17. The decoder of claim 15, wherein: the multimedia file includes atleast one audio track accompanying the sequence of encoded video frames;and each reference to an encoded video frame in the abridged indexincludes a reference to a portion of at least one of the video tracks.18. The decoder of claim 15 wherein the processor is configured toidentify a desired encoded video frame; determine the encoded videoframe that is closest to the desired video frame in the abridged index;and display an encoded video frame.
 19. The decoder of claim 18,wherein: each reference in the abridged index to an encoded video framealso includes a reference to the portion of the complete index thatrefers to that encoded video frame; and wherein the processor configuredto display an encoded video frame, further comprises: the processor usesthe reference to the encoded video frame in the abridged index that isclosest to the desired encoded video frame to locate that encoded framewithin the complete index; the processor searches in the complete indexfor the desired encoded video frame; and the processor displays thedesired encoded video frame.
 20. The device of claim 19, wherein theclosest frame is the closest preceding frame in the sequence to thedesired frame.
 21. The device of claim 18, wherein the processorconfigured to an encoded video frame further comprises the processordisplaying the encoded video frame that is determined to be closest tothe desired video frame.
 22. The decoder of claim 15 wherein theprocessor is configured to locate and playback the sequence of encodedvideo frame without receiving the complete index.
 23. The decoder ofclaim 15 wherein trick play functionality comprises at least one of fastforward, rewind and scene skipping.